I wonder if DLP projectors aren't limited in their on/off contrast ratio by their basic optics. First is a manufacturing issue. How low RMS surface roughness can TI achieve in an electroformed micro mirror? A mirror surface that scatters still scatters when it is tilted to make black projection. Second is a diffraction issue. The small 10 micron mirror size means that more than 2% of the light striking the mirror diffracts at angles more than 55 degrees away from the geometrically expected direction. So the tilted mirror can't make black projection.
Has TI found clever ways around these two issues?

I've just noticed that the Epson Home Cinema 6100 3 DLP projector yields 18,000:1 on/off contrast, so my first post might be amiss.

Is it possible that digital projectors "cheat" the (sequential) on/off contrast test by, for example, closing a shutter whenever all pixels are at zero? Shouldn't off/on contrast be measured in a more aboveboard way as follows:
Just as ANSI contrast uses a 50% white target, make ANSI(x) contrast use an x% white target. Then on/off contrast is measured as the limit, as x approaches 0, of ANSI(x) contrast.

Apparently the limit so far for DLP is 2,500,000:1 on/off contrast.

http://www.zeiss.com.mx/c12567b00038cd75/Contents-Frame/c08a81c281285b70c125748300488f70


A Carl Zeiss in-house design, VELVET fascinates not only by its measured contrast ratio of 2,500,000 : 1 – a tremendous leap compared to other projectors offering up to 30,000 :1

I heard, from Ohlson, it can achieve this by using two DLP panels rated at 30,000:1 aligned in series.

I've just noticed that the Epson Home Cinema 6100 3 DLP projector yields 18,000:1 on/off contrast, so my first post might be amiss.

That's an LCD.

But the Planar 8150 can do (measured) on the order of 17,000:1. And some who have seen it have said the Sim2 Lumis Host can do better than the JVC RS20 in terms of CR.

Is it possible that digital projectors "cheat" the (sequential) on/off contrast test by, for example, closing a shutter whenever all pixels are at zero?

Yes, many DLPs are now using Dynamic Iris (what TI calls Dynamic Black), to improve on their native/simultaneous CR. But that's not (necessarilly) cheating. The Epson you mention above uses it as well.

Shouldn't off/on contrast be measured in a more aboveboard way as follows:

There's nothing "below board" about a DI, it's just a technology like any other. When implemented well it can do wonders for dark scenes that would otherwise look milky/foggy, without introducing any noticeable artifacts.

Just as ANSI contrast uses a 50% white target, make ANSI(x) contrast use an x% white target.

The ANSI measurement doesn't use a 50% white target, it uses a grid of 100% white blocks covering 50% of the field.

Then on/off contrast is measured as the limit, as x approaches 0, of ANSI(x) contrast.

You can't use <100% White very easily because then the projector's gamma starts coming into play.

I suggest you read Mark Peterson's Contrast thread (link in the "Popular Threads" sticky)

"Has TI found clever ways around these two issues?"

This is a black/white view, i.e., once around it's not an issue.

The issues are ever present and their detrimental effects being continuously worked on and reduced.

"I heard, from Ohlson, it can achieve this by using two DLP panels rated at 30,000:1 aligned in series."

All it (2,500,000:1) takes is two 1600:1 panels in series.

There's no DLP that does 30k:1.

Also, the Zeiss rating might be based on the use of lasers, which if scanned give the possibility of much higher CR because there's only a pinpoint beam to scatter light.

The ANSI measurement doesn't use a 50% white target, it uses a grid of 100% white blocks covering 50% of the field.

You misunderstood my ambiguous expression. By "50% white target" I mean 50% of the target area is white. By "x% white target" I mean x% of the target area is white. My proposed limit definition runs into no gamma issues, and provides a valuable datum. It probably agrees with sequential on/off contrast with DI turned off in most cases. But can DI and all other "enhancements" be turned off when we want to know that answer? Also in cases where the limit doesn't agree with the pure sequential measurement, which value do we prefer? If, for example, the all white screen can't reach its full white luminance for power reasons, why are we even measuring the all white screen? Better to use the limit definition.

You misunderstood my ambiguous expression. By "50% white target" I mean 50% of the target area is white. By "x% white target" I mean x% of the target area is white. My proposed limit definition runs into no gamma issues, and provides a valuable datum.

That's exactly what the test patters used by Mark Peterson in the above mentioned Contrast thread do. They measure CR with varying percentages of full white on the screen and give a very good picture of the "curve" of CR vs scene brightness.

It probably agrees with sequential on/off contrast with DI turned off in most cases.

With non-DI projectors it does, actually in the case of the JVCs and probably displays like Plasmas and maybe CRTs, it actually comes out higher because a very small white area can be brighter than a full white field.

But can DI and all other "enhancements" be turned off when we want to know that answer?

The % white area, or as Mark was calling it "0% Simultaneous CR" measurement tells you exactly what the "Native" Contrast of the projector is, whether DI is on or not, because it is measured in such a way as to have the IRIS in a fixed position for the black and white measurements.

Also in cases where the limit doesn't agree with the pure sequential measurement, which value do we prefer?

Any DI-equipped PJ will have a different value for On/Off and the "0%" measurement. That's the purpose of a DI. But we don't "prefer" either, they are both valuable pieces of information in characterizing the performance of the display. Both tell us something about how the projector performs.

I heard, from Ohlson, it can achieve this by using two DLP panels rated at 30,000:1 aligned in series.

Thank you for this fascinating information. It is the same way a double monochromator (probably pioneered by Zeiss) reduces the stray light due to a single monochromator. It is a very expensive solution and it will make the ANSI contrast worse since it introduces an image relay lens.

Also, the Zeiss rating might be based on the use of lasers, which if scanned give the possibility of much higher CR because there's only a pinpoint beam to scatter light.

The scattering I calculated is due to the size of the individual mirror, about 10 microns square. Making the laser spot much smaller than the mirror doesn't decrease, but rather increase, the scatter.

Anyhow the laser can only be used in the first series stage.

The instantaneous CR is limited by the reflectivity from the back surface and the diffraction efficiency. The diffraction efficiency can be calculated directly in closed form by modeling the system as a two dimensional array of micromirrors tilted by an angle B along a diagonal axis. most of the scattering comes from the pixel corners and smaller pixels give rise to more scattering but denser pixels give rise to less scattering from the back surface.

for a 9.7 micron pixel CR from diffraction is around 65000/1 so back surface reflectivity is the limiting factor and improving the titanium nitride antireflection coating and increasing the packing density will improve the DLP contrast ratio the most.

mlang46, I didn't consider "reflectivity from the back surface" (meaning what the light finds that misses the mirror) because this isn't an ultimate limiter. You can have deep light traps down there, or as you say, make the mirrors almost touch.

You're right that the diffraction from a square aperture is weakest in the diagonal directions, but this can't be sustained for arbitrarily small apertures. The TI mirrors are already less than 20 wavelengths across. I don't know at what point "easy" Fresnel-Kirchoff diffraction calculation must be abandoned. Do you know?

"Making the laser spot much smaller than the mirror doesn't decrease, but rather increase, the scatter."

I meant the illumination source is a tiny beam, as opposed to flood illumination of thye entire microdispaly.

I meant the illumination source is a tiny beam, as opposed to flood illumination of thye entire microdispaly.

(Hey, I would have expected a guy named Noah to not be afraid of floods.)

What I pointed to is the diffraction by each single mirror. They're simply too small to reflect light according to geometry. Whether the whole chip is illuminated at once or the mirrors illuminated one at a time, the degree of diffraction is practically the same. Now when you tilt the little mirror to make black, a fraction of the reflected light still gets into the aperture where it went when the mirror was untilted. I think mlang46 is saying the fraction is 1/65000.

The size of the illumination source has nothing to do with this. An illumination source can be large but convergent, so its light would come to a point (or fill an aperture) after bouncing off any one of the little mirrors, if not for the diffraction.

My proposed limit definition runs into no gamma issues, and provides a valuable datum. It probably agrees with sequential on/off contrast with DI turned off in most cases.Pretty much. It is a valuable datum, but in one way doesn't provide the valuable datum the on/off CR as done now does (assuming the display is in a reasonable mode). Your's would be pretty close to what most call native or static on/off CR. It is useful, but dynamic on/off CR with a good DI is also useful.

Using the Planar 8150 as an example, it basically has native on/off CR in the 3k:1 range and dynamic on/off CR in the 15k:1 range. The 15k:1 dynamic isn't as good as 15k:1 native would be, but the projector also isn't as weak as only being able to do 3k:1 on/off CR total would be.

Using this calculator:

http://home1.gte.net/res18h39/contrast.htm

Your proposal is similar to leaving everything as is except for reducing the "% of screen area covered by checkerboard" and then only looking at the 100% row. While that is useful, the advantage of the DI comes in with things like the 5%, 10%, and 20% rows, whether the % of screen area has been reduced on not. This is because those things don't have white. If the on/off CR test was changed to what you propose then the advantage for those kinds of scenes of the DI would be lost in the implications of the numbers. I think giving both native and dynamic on/off CR is a pretty good solution, but it does depend on being able to get those.

--Darin

The question to me is what is the native on\off limit of a single chip DLP projector? A DI could be used to reach a very high on\off, much higher than 17,000 though one might not like the effects of the DI in operation. What is the native on\off of the DC4 chip. Is that even the right question since I doubt but don`t know if the spec is to the chip the light engine or the light engine plus lens. I suspect it is the later and very much depunds on the color wheel and variable lamp dimming.

"The size of the illumination source has nothing to do with this. An illumination source can be large but convergent, so its light would come to a point (or fill an aperture) after bouncing off any one of the little mirrors, if not for the diffraction."

The diffraction isn't the only thing that limits CR; my point is that the illumination of the panel can contribute more or less scatter.

The diffraction isn't the only thing that limits CR; my point is that the illumination of the panel can contribute more or less scatter.

The strand began with two contributing factors: surface roughness of the small mirrors and diffraction by the small mirrors. Mlang46 added a third factor, reflection by the back surface (behind the mirrors). Are you mentioning a fourth factor? Then please describe what it is.

Just the simplest and most ubiquitous CR reducer of all - scattered light, which occurs everywhere.

A mirror surface that scatters still scatters when it is tilted to make black projection.There may be a white paper around showing an image, but from what I recall the main part of the mirror surface could do very well at not reflecting toward the lens. Going along with what mlang mentioned, what I recall is that a picture showed that there were 5 points on each mirror that were the biggest problem for CR. Each of the 4 corners and the dimple in the center showed up as very bright on the picture I recall. TI has been working on the dimple, but I don't know how far they have gotten as far as its contribution to CR reduction.
What is the native on\off of the DC4 chip.First, I believe Greg Rogers mentioned that he likes to use static instead of native because it can depend on the iris position (or irises). I think the Marantz 11S2 can get up to around 10k:1 on some machines with both irises shut down a fair amount. They might be able to go higher with more closed irises (less light getting through), but I don't know how much further those irises could be closed without creating an issue. The chip itself could probably do a fair amount over 10k:1 just considering light coming in from a particular angle and then light going toward the lens, but I don't know how much higher. In experimenting with the Optoma H79 years ago I ended up at about 9k:1 and figured the chip itself could do about 11k:1 with very closed irises from my measurements, but with bad uniformity problems from those irises being too small.

--Darin

DLP has a system stuggled to reach 10k:1 native.
By combining two systems in a series you get a multplicative effect on contrast.
I am pretty sure the Velvet is the real thing. It impressed planetarians with an invisible blend zone. This indicates very high native system contrast.

Just the simplest and most ubiquitous CR reducer of all - scattered light, which occurs everywhere.

Precisely what light is scattered by what? What assumptions are you making? Just because a light is shone over the whole DLP chip rather than onto individual mirrors, doesn't imply that the light is shone over more than the whole DLP. The illumination can be designed to slightly overfill the chip and a simple black aperture mask catch the spill. What projector maker doesn't do at least this?

A scanning laser would improve contrast or reduce scatter versus a bulb, due to the fact that a scanning laser switches off whilst passing a "off" or "black" pixel.
This means ANSI contrast would improve as dark areas of the picture wouldn't have as much scatter due to the laser turning down or off etc.
A fade to black scene would mean the laser not firing at all giving perfect blacks.
The question is, how easy is it to get a laser to scan a DMD at a per pixel level?(at varying refresh rates)
And then provide grey scale illumination? (PWM?)
Finally, would three chip or single (RGB laser(s)) chip be easier?

DLP has a system stuggled to reach 10k:1 native.
By combining two systems in a series you get a multplicative effect on contrast.

The multiplicative effect applies only to sequential contrast, not to ANSI contrast. In a series configuration there is a relay lens imaging the first chip onto the second chip. Assume for simplicity that the mirrors are pixel by pixel synchronized on the two chips. Naturally when both chips have all mirrors tilted to "off", and fraction F of the light reaching the first chip goes where it shouldn't go -- into the relay lens -- to reach the second chip, only fraction F² reaches the next aperture, for projection. Hence the multiplicative effect for sequential contrast.

Now consider what happens when half the mirrors are tilted to "on" and half to "off". All the "on" mirrors send their reflection into the relay lens. We can ignore the tiny extra amount of light from the "off" mirrors, because the relay lens is going to send much more of the light from the first chip's "on" mirrors onto the second chip's "off" mirrors than the first chip's "off" mirrors send onto the second chip's "off" mirrors. The relay lens has at least 8 glass-to-air surfaces and is not immune to the veiling glare from all complex lenses.

So the second chip receives much light onto its "on" mirrors and a bit onto its "off" mirrors. For the sake of the final ANSI contrast this is insignificantly better than if it had received much light onto all its mirrors. This is because, again, the light from the second chip's "on" mirrors, misimaged by the flarey projection lens, illuminates what should be the black pixels on the screen by orders of magnitude more than what that same amount of light on the second chip's "off" mirrors could contribute to the black pixels on the screen.

To good approximation, the DLP series design has no effect on ANSI contrast. (My earlier suggestion that it reduces the ANSI contrast was based on faulty analysis.)

In a planetarium application, ANSI contrast is irrelevant. The average projected luminance will be less than 1% of the white projected luminance. But whoever makes a DLP series design projector for movies will have to struggle like everyone else to improve the ANSI contrast.

To good approximation, the DLP series design has no effect on ANSI contrast.That is likely pretty reasonable for the most part. If a projector is getting say 3000:1 native on/off CR and 700:1 ANSI CR then not all that much of the black level in the ANSI CR test is going to be reduced by not lighting up those mirrors. Whether it is "no effect" could be debated in that case as it may be 20% difference or so. For a case like irises closed on a DLP getting say 8000:1 on/off CR and 700:1 to 1000:1 ANSI CR, the percentage would be lower and could be looked at as "no effect" even more.

What it would likely affect is simultaneous CRs that many people seem to think ANSI CR indicates performance for, like a little bit of white and lots of black (like the planetarium thing you mentioned). While ANSI CR may hardly move, the CRs for those those kinds of things could go up a lot.

While I would be happy if manufacturers increase ANSI CR, with where DLPs have gotten I don't know how much improving it will matter, especially if they get CRs up for the small amount of white and lots of black cases. They are already way beyond what CRTs tend to do for ANSI CR and I suspect way beyond film. And as far as rooms go I think it tends to be much harder for people to modify their room to retain ANSI CRs above 700:1 than on/off CRs even of 100k:1 or higher (at least at night), since the later just requires extinguishing other light sources while the former requires doing things about reflections.

--Darin

"Precisely what light is scattered by what?"

It's puzzling that you dispute the obvious when you started off the discussion with 2nd-order effects.

As you pointed out no surface is a perfect reflector, and all light hitting any surface has some % of scatter.

It's puzzling that you dispute the obvious...

I can't dispute what you say becauxe it doesn't make an ounce of sense to me.
To repeat: The strand began with two contributing factors: surface roughness of the small mirrors and diffraction by the small mirrors. Mlang46 added a third factor, reflection by the back surface (behind the mirrors). Then I explained that the illumination will only fall on the chip.
What are we overlooking? "Just the simplest and most ubiquitous CR reducer of all - scattered light, which occurs everywhere", you say. Didn't Mlang46 and I already dissect that into three parts? Do you know a fourth part?

you started off the discussion with 2nd-order effects

Hey! Is your fourth part not a 2nd-order effect?
Of course these are 2nd-order effects, and we ignore 3rd and higher order effects (like backscatter from the projector lens). Do you imagine that contrast ratios in the tens of thousands are going to involve 1st-order effects?

The original post:
"... lasers, which if scanned give the possibility of much higher CR because there's only a pinpoint beam to scatter light."
Why is the total scatter at all different if a small intense beam scans over the mirrors or if a weaker big beam illuminates all the mirrors at once? The scatter is actually slightly greater (due to diffraction) if the laser underfills the mirrors, while slightly less (due to the the back surface reflections noted by Mlang46) if the laser skips the cracks between the mirrors. Are you imagining that the laser skips all the mirrors that are tilted to make black? That would be one tricky laser rastering, and what happens for tones between white and black?

I can't dispute what you say becauxe it doesn't make an ounce of sense to me.
To repeat: The strand began with two contributing factors: surface roughness of the small mirrors and diffraction by the small mirrors. Mlang46 added a third factor, reflection by the back surface (behind the mirrors). Then I explained that the illumination will only fall on the chip.
What are we overlooking? "Just the simplest and most ubiquitous CR reducer of all - scattered light, which occurs everywhere", you say. Didn't Mlang46 and I already dissect that into three parts? Do you know a fourth part?

Scattering in the optics?

Scattering in the optics?

We're considering sequential contrast ratio. Forward scattering in the optics will be the same for the white signal and the black signal and cancel out in the contrast ratio.

Back scattering by the optics was mentioned in my last post. It makes negligible contribution because whatever is scattered back must be scattered again forward, and into the lens, and be projected within the image area. (Of course back scatter will be no different for the laser scanned chip or the fully illuminated chip, which it was noah katz's original purpose to differentiate.)

"The strand began with two contributing factors: surface roughness of the small mirrors and diffraction by the small mirrors. Mlang46 added a third factor, reflection by the back surface (behind the mirrors)."

What do you suppose would happen to the CR if all the surfaces after the DMD, except the light trap for the off state, were white (which I would refer to as a 1st-order effect)?

Some of the light diffracted from the mirror edges goes down the optical path directly, but a lot of the rest could be absorbed by good optical system design.

"Why is the total scatter at all different if a small intense beam scans over the mirrors or if a weaker big beam illuminates all the mirrors at once? "

My error, you're correct on that point.

Though I'm not sure of the basis of your claim that " the illumination will only fall on the chip."; that might be done with a mask, but not perfectly i.e. more scattered light somewhere.

Noah, the strand begins with the sentence: "I wonder if DLP projectors aren't limited in their on/off contrast ratio by their basic optics." We're not concerned with silly errors, like painting surfaces white that obviously should be black, but with hard-to-avoid limits. It's a design of tiny mirrors trying to direct light in and out of a lens. What limits does this basic design impose? I fear you diverged from the context.

A scanning laser would improve contrast or reduce scatter versus a bulb, due to the fact that a scanning laser switches off whilst passing a "off" or "black" pixel.
This means ANSI contrast would improve as dark areas of the picture wouldn't have as much scatter due to the laser turning down or off etc.
A fade to black scene would mean the laser not firing at all giving perfect blacks.
The question is, how easy is it to get a laser to scan a DMD at a per pixel level?(at varying refresh rates)
And then provide grey scale illumination? (PWM?)

Fulabeer, I'm sorry I didn't see your post (because it appeared at the same moment as one of mine), and 27 hours later I made essentially your same speculation.

We're considering sequential contrast ratio. Forward scattering in the optics will be the same for the white signal and the black signal and cancel out in the contrast ratio.With an iris in the lens I'm not sure it would cancel out. I would have to think about it some more, but in the Optoma H79 I modified the light for white and the light for black had very different properties at the plane where the iris went. Basically, the white was pretty focused in the area of the opening of the iris, while black was more random. It could be that this scattering would have a small effect that would be negligible though.

--Darin

"It's a design of tiny mirrors trying to direct light in and out of a lens. What limits does this basic design impose? I fear you diverged from the context."

OK, I plead guilty; the scatter I was talking about applies to all pj's, not just DLP's.

With an iris in the lens I'm not sure it would cancel out.

You're right. I hadn't considered that the iris opening would change between the frames. I can NEVER consider allowing that in the measurement of on/off contrast because any projector could completely close its iris on an all black frame and so elevate its contrast ratio to infinity. Complete closure mechanical irises exist. Or the projector can shutter the front of the lens.

... but in the Optoma H79 I modified the light for white and the light for black had very different properties at the plane where the iris went. Basically, the white was pretty focused in the area of the opening of the iris, while black was more random. It could be that this scattering would have a small effect that would be negligible though.

The classical condensing illumination system focuses the light source into the plane of the iris. That way there is practically no waste of light. Since it's very bright there, your eye can't notice the weak light spread farther out on the plane of the iris. All the high spatial frequency information in the image on the chip goes out there. (That's a desirable kind of scatter.) Also the mis-aimed illumination due to errors and scatter in the condensing system is there. Also some of the projection lens ghosting is there. But they're all too weak to notice next to the bright spot. You'd have to make measurements in that plane to detect it. When the mirrors are turned to make black this destroys the mirror which reflects the image of the light source into the plane of the iris. So when you examine the iris plane there are only the weak effects to see, and they're visible.

OK, I plead guilty; the scatter I was talking about applies to all pj's, not just DLP's.

Nope, you can't plead guilty to what no one accused you of. If you identified a contrast reducing factor in DLP projectors which made the factors the rest of us identified insignificant, then that would have been interesting. But by saying "suppose...all the surfaces after the DMD, except the light trap...were white" you're not pointing to a factor in play. The surfaces aren't white. It's fair to assume that all the obvious contrast reducing factors have been dealt with by TI and the DLP projector makers by now, so we concentrated on stubborn factors. I should have listed 4 factors, not 3. Darinp2 mentioned unflatness in the TI mirrors. The diffraction spreading off a 10 micron mirror is much greater than the geometric abberation due to even considerable curving. But if there's a damned dimple in the mirror, as darinp2 reports, that could matter. And it might be a toughie for TI to cure.

I understand mlang46 to be reporting that the diffraction by the 10 micron mirror sends 1/65,000 of the light intended for the light trap into the lens. If this is accurate, it's not the major factor. If someone can provide me with dimensions, I'd like to verify the diffraction calculation. We lack numerical estimates for the other three factors. You might even be right that some garden-variety, seemingly easily corrected factor is presently mattering more than the 4 factors we discussed, but throwing out explanations such as "scattered light, which occurs everywhere" only works for fairy princesses.

You're right. I hadn't considered that the iris opening would change between the frames.I was referring to an iris that is static. The size, shape, and placement of this iris is very important to the CR of the light coming out of the projector, because the light going through the plane of the iris tends to be different for white than for black. TI has a white paper about this and going from 10 degree mirrors to 12 degree mirrors. The 12 degree mirrors helped separate some of the "bad" light from the "good" light in a way that would allow the iris to be more open without getting too much of the "bad" light, but I'm not sure where that paper is. I do recall that the light from the DMD in a plane in the lens where an iris could go could look like 2 coins overlapped, with one of the coins representing light that would raise the lumens for white if the iris was open enough, but would hurt the static on/off CR because it would let proportionally more light through for a video black image than a video white image. With the 10 degree mirrors the 2 coins of light had more overlap than with the 12 degree mirrors.

Closing just the lens iris down in something like the Sharp 20k would increase the on/off CR a significant amount (while decreasing white a significant amount). Closing both it and an iris before the DMD down would increase on/off CR even more (and without much extra drop in white level). Closing both down and leaving them there could increase the resulting on/off CR over 2x.
I can NEVER consider allowing that in the measurement of on/off contrast because any projector could completely close its iris on an all black frame and so elevate its contrast ratio to infinity. Complete closure mechanical irises exist. Or the projector can shutter the front of the lens.If you don't consider what a dynamic iris does then you have left out very useful information, as I explained before. If an iris could close completely and do it so well as to not be noticeably different than a static iris with infinite on/off CR, then it would be basically the same. The main reason they can't close an iris now for infinite on/off CR is because they don't have enough native or static on/off CR to be able to do that without causing bad side effects. Basically, if measurements are done in a mode that works well then they are valid, although it is good to give both native/static on/off CR and dynamic on/off CR, as this helps in explaining what is likely to happen.

Put another way, if a person takes your stance that they can't consider what a dynamic iris does and can only look at what the on/off CR is with no iris movement, then they would end up being wrong if they tried to figure out how much the Planar 8150 with 3k:1 native on/off CR and 15k:1 dynamic on/off CR could do with an image where the brightest thing is 10%stim (10 IRE with 0 base or 10% video level) while maintaining a standard gamma and if they only looked at the 15k:1 on/off CR they would end up being wrong if they tried to figure out how much CR it could do with a small white spot on a black background.

A person could use this calculator:

http://home1.gte.net/res18h39/contrast.htm

to do some estimates of what a 3k:1 on/off CR projector would do vs the Planar for say a checkerboard with 10%stim for the brightest rectangles while maintaining a 2.5 gamma, assuming some ANSI CR and room gain. Using ANSI CR of 600:1 and room gain of 0.005 (enough to lower the ANSI CR off the screen to 240:1), according to that a 3k:1 on/off CR projector with no DI (or the DI disabled) would give about 19:1 in that image, but the Planar with its dynamic iris and about 15k:1 dynamic on/off CR could do about 56:1 in that image.

The effect above can be clearly seen on lots of images. When I was at Alan's we paused a dark scene in Alien vs Predator and went between DI enabled and disabled. The difference was significant, with the DI on case looking much less washed out and more dimensional.

--Darin

I was referring to an iris that is static.

You're right again. I was sloppy to say: "forward scattering in the optics will be the same for the white signal and the black signal and cancel out in the contrast ratio." Most of white signal should reach the lens in a nice beam while of the black signal, spurious as it is, reaches the lens less orderly. You're certainly right that the scatter ratios for the two will therefore be different.

the light from the DMD in a plane in the lens where an iris could go could look like 2 coins overlapped,

Did you observe this with the lens removed? Then it's invalid, since the iris plane is optically displaced by the lens elements before it. In other words, the two coins could have been converged into one when their light finally reached the iris.

Why are there two beams at all? Why does range of tilt angle change the convergence of the two beams, since the mirrors are all at one angle or the other for the sequential test?

Are there good diagrams available for these systems, or are the various 1-DMD projectors of very different optical construction?

Did you observe this with the lens removed?Only the lens elements after the one with the iris. This is how I decided how to design the iris I put in. I put a white piece of paper in the same plane as the iris to see what the light looked like as it hit that plane. With an Optoma H79 I was able to get about 9k:1 on/off CR a few years ago, with enough light to get around 6 ft-lamberts for white off my screen. I wrote something up about how I did it. I basically used 4 irises. Two before the DMD and 2 in the lens (each pair in the same plane). One iris was basically white and one red in a way that got things close to D65. The on/off CR was higher for blue and green than for red, but this worked pretty well as I find it harder to see red in very dark images and did not see a color shift for blackouts like I would if they leaned heavily toward blue or green.
Why are there two beams at all?I'm not sure, but there is a white paper from TI that talks about it and I just don't recall enough about it. I think they referred to one of them as coming from either a "neutral" of "off" positions of the mirrors and the other one (the one you want) coming from the on positions. I could have that wrong, but in the Optoma H79 it basically looked two overlapping coins where one was white and one was magenta. I don't know why the "bad" light looked magenta.
Why does range of tilt angle change the convergence of the two beams, since the mirrors are all at one angle or the other for the sequential test?I'm not sure, but I could have been more clear that the 2 coins thing is only for white source images. For a blackout image the light in the lens at the plane of the iris looked much more random.
Are there good diagrams available for these systems, or are the various 1-DMD projectors of very different optical construction?There are some variations, but probably a fair amount of commonality. The TI paper I recall talked about a couple of different approaches.

--Darin

This is how I decided how to design the iris I put in.

I'm impressed that you got in there and accomplished that.

in the Optoma H79 it basically looked two overlapping coins where one was white and one was magenta.

R,G,B output in one direction and just R,B output in a second direction! I would look at the prism system for an explanation.

If you don't consider what a dynamic iris does then you have left out very useful information, as I explained before.

The information is only about what black will appear in an all black frame. We can't guess what black will appear in any other frame, because we don't know what the DI function does to any other frame. If projector makers published their DI functions then we could estimate what black would appear in those.

The main reason they can't close an iris now for infinite on/off CR is because they don't have enough native or static on/off CR to be able to do that without causing bad side effects.

True there are lots of all black frames in movies, not just in sci-fi and nightmare movies. Some editors like to fade out and then fade in. Some white-on-black titles frames are separated by black frames. A visual jump in such places would be ugly. But different projector manufacturers will have different tolerances for this ugliness. And the phenomenon isn't limited to infinite DI CR. Why not 30,000:1 DI CR too? Again, we need to know the DI function for DI CR to be informative.

A person could use this calculator:

That calculator requires that the entered FOFO contrast ratio -- great name! -- be unaided (without DI). As I understand the underlying calculation, it would be nonsense using the DI CR. After the calculation, you could multiply the luminances outputted by the value of the DI function for the particular checkboard, if the function were known.

we paused a dark scene in Alien vs Predator and went between DI enabled and disabled. The difference was significant, with the DI on case looking much less washed out and more dimensional.

Dark scenes in the world are dreary and are not fully 3-dimensional. We're getting off-topic.

dcouzin,

You really should read this thread:
http://www.avsforum.com/avs-vb/showthread.php?t=852467

"If someone can provide me with dimensions, I'd like to verify the diffraction calculation."

What dimension other than the 10 micron mirror size which was mentioned?

Do you not need to know how sharp the corners of the mirrors are, or is it a given that it must be too small compared to the wavelength to matter?

R,G,B output in one direction and just R,B output in a second direction! I would look at the prism system for an explanation.The H79 is a single chip DLP where the color primaries are separated by the colorwheel. I'm not sure how a prism would come in as far as this one.
The information is only about what black will appear in an all black frame.The same argument could be made for any spec. The white point is only about the white point on a white image, the color primaries are only about the color primaries with only one color primary at a time, the gray (or RGB) balance is only about gray in images with just one level of gray, the ANSI CR is only about black and white in that particular image, etc. But they are all indicators.
We can't guess what black will appear in any other frame, because we don't know what the DI function does to any other frame.You do need to know how it works and I used an example where I know basically how it works for the case I gave (the Planar 8150 with only fairly dark stuff). You said that the operation of the DI can never be allowed for on/off CR and as I explained, you would then end up wrong about predicting what would basically happen with certain scenes.
If projector makers published their DI functions then we could estimate what black would appear in those.They don't need to publish them because we can investigate what they do ourselves. I know that the Planar basically compensates for the iris closing down for things above video black. That is, if the iris shuts the light down 50% for an image with no bright stuff, then gamma will be adjusted so that levels like 10%stim end up close to where they were before the iris shut down. Using .5 * 2 = 1, .4 * 2.5 = 1, etc. Video black is left at what the iris can shut it down to, thus increasing intra-image CR for lots of images.

The Sony system works much differently than the Planar system and so I wouldn't have assumed the same compensation. It doesn't completely compensate as the iris is shut down (at least it didn't in my testing with the Sony VW80).
But different projector manufacturers will have different tolerances for this ugliness.And we will have different tolerances. If we calibrate to a mode that works well (our decision, not the manufacturers) then it is relevant. It isn't the specs as claimed by the manufacturers that really matter, but what happens when people set the projector up. Some reviewers are of course more trusted than others to get things setup well and then report the actual results.
And the phenomenon isn't limited to infinite DI CR. Why not 30,000:1 DI CR too?Why not? The Sony VW80 can do that 30k:1 with a DI and around 6k:1-10k:1 static on/off CR from my memory (I would have to go back to my measurements to get closer figures). Experience over the last few years has shown that a multiplier from static on/off CR to dynamic on/off CR can be up to around 3x to 5x before more harm is caused than good for most people. A very respected reviewer (Greg Rogers) mentioned in one of his recent reviews that he thought that Sony DI implementation was good enough that he didn't imagine many people would run the projector with the DI off (or something to that effect).
Again, we need to know the DI function for DI CR to be informative.No disagreement there. What I disagreed with was your assertion that iris movement could never be taken into account with respect to on/off CR. It needs to be taken into account, including the implementation, if a person will use it. And I think the percentage of people who leave a DI on is way higher than the percentage who leave it off, especially with the better implementations (Planar, Panasonic, and Sony at least).
That calculator requires that the entered FOFO contrast ratio -- great name! -- be unaided (without DI). As I understand the underlying calculation, it would be nonsense using the DI CR.I believe the calculator was put up before DIs came along. For the brighter values (like 100%) the unaided value should be used. For values like I put in my post about the Planar the aided (with DI) value can be used because of the way the Planar iris works (from talking to the main engineer for that feature on that projector and from what a friend who did some measurements has told me about his results).
After the calculation, you could multiply the luminances outputted by the value of the DI function for the particular checkboard, if the function were known.For the cases I gave the numbers for, what luminances values are you proposing multiplying? There is luminance for the brighter rectangle and luminance for the video black rectangle, which comes from a combination of the black floor and the washout best characterized by ANSI CR. It doesn't take into account that ANSI CR can be different with different iris positions, but that probably isn't a huge effect for the example I gave.

--Darin

What dimension other than the 10 micron mirror size which was mentioned?

The basic optical geometry: degree of collimation of illumination on mirror; angle of tilt during black; axis of tilt; angular size of lens pupil.
The mirror tilted for black makes its diffraction pattern and we want to calculate how much of this gets into the lens.

The H79 is a single chip DLP where the color primaries are separated by the colorwheel. I'm not sure how a prism would come in as far as this one.

Oops, I thought it was 3 chip.
The explanation does seem to involve the mirrors having two different (but close) "on" angles. The mirrors are flapping during white projection (in order to balance R,G,B). Can the length of time that the mirror is at "off" affect where it returns to for "on", hysteresis-like? Was there any hint of a third spot in the iris plane?

Why the focus on DLP? Wouldn't the same techniques work with LCOS for even better results than DLP? The same way the Velvet gets 2.5 million to 1 contrast with two panels in series, couldn't the same be done with two 3-chip LCOS?

I'm a CRT guy myself, but LCOS (especially SXRD) seems to my eye to be closest to CRT. LCOS has better motion, I notice blur less on SXRD than DLP, while DILA LCOS from JVC is worse than DLP! DLP also looks not as saturated as LCOS/SXRD. The colors seem muted and the screen flickers with DLP for me, even with 3-chip. I see color separation with both 1-chip with a wheel and LED, and with 3-chip.

Also natively, LCOS/SXRD has more contrast on/off than DLP can currently do, without resorting to tricks the Velvet does.

The same way the Velvet gets 2.5 million to 1 contrast with two panels in series, couldn't the same be done with two 3-chip LCOS?

I've assumed the Velvet consists of two 1-chip DLP's in series. 3-chip projectors, whether DLP or LCoS, are extremely difficult to put into series. The first three chips are illuminated each with R,G,B. Through prisms the projection lens conveys the three as if one. In a series design, a relay lens replaces the projection lens. What will the relay lens relay onto? The R,G,B needs to be reseparated before reaching focus. That requires a prism system between the relay lens and the second three chips. And then how will these chips be conveyed to the projection lens? That requires another prism system and there's nowhere to put it.

I've assumed the Velvet consists of two 1-chip DLP's in series.

That sucks. :( So that means the Velvet will be more prone to RBE? You can see RBE more easily when a moving object moves between two extreme contrast zones? If that's the case, RBE will be a nightmare on the Velvet considering it has 2.5 million to 1. I'm very sensitive to RBE and can even see color separation of a three tube CRT!

I've verified that the Velvet consists of single DLP's in series. Since it uses TI BrilliantColor, the quasi-rainbows will have three extra colors. More fun for you.

RBE is due to rapid eye movements, not image movements (although the eye might dart to follow an image movement).

"In a series design, a relay lens replaces the projection lens. What will the relay lens relay onto? The R,G,B needs to be reseparated before reaching focus."

The first three have already generated the colors, so only a 4th is needed 4th to modulate luma.

I've verified that the Velvet consists of single DLP's in series. Since it uses TI BrilliantColor, the quasi-rainbows will have three extra colors.TI's BrilliantColor can be done with just 3 primaries. That seems to be the most common from what I've seen. I'm not sure how many add a yellow segment to the colorwheel (not a lot in home theater models is my guess even though it sounds like one NEC has that), but I can't think of any that have cyan or magenta segments.

--Darin

Zeiss Velvet
2DLP, 2MPixels, 2,5M:1

JVC
4LCOS (3*4K for color, 1*8K luma), 35 MPixels, 1.1M:1

The concept can be implemented in many ways
2DLP, 1+1
4DLP, 3+1
1DLP +1LCD
4LCD, 3+1
6LCD, 3*2, 2 in series for each color
3LCOS +1LCD
4LCOS

LCOS might reach a contrast limit that is due to how well the polarization can be controlled. 2DLP can perhaps have a greater efficiency in using theoretical contrast potential.

Brightside published pdfs and xls-files illustrating many of the concept designs I listed.

"6LCD, 3*2, 2 in series for each color"

This one is interesting; if the panel pairs can be gotten close enough together, they could act as single high-CR panels and eliminate the need for the relay optics.

Better yet, integrate both panels into a single device.

The first three have already generated the colors, so only a 4th is needed 4th to modulate luma.

You're right! But not quite as you describe.
The first three chips have already generated the chromaticity and the luminance. (If they were just used to generate a constant luminance chromaticity then they would make no black and be useless for the purpose of the series.) Consider LCoS first. A fourth chip can't modulate luminance or else the luminance signal would get squared. So the fourth chip needs to be at 100% at all pixels except those pixels which have R=G=B=0 from the first three chips. For DLP, it depends on how the oscillations are done in the first 3 chips whether the 4th chip can be at anything but constant "on" except for those pixels which have constant "off" on all three earlier chips.

So the fourth chip works as a purely black level suppressor, which is the main goal of the series design.

TI's BrilliantColor can be done with just 3 primaries. That seems to be the most common from what I've seen. I'm not sure how many add a yellow segment to the colorwheel (not a lot in home theater models is my guess even though it sounds like one NEC has that), but I can't think of any that have cyan or magenta segments.

Sorry I based this on a press release which had scrambled "BrilliantColor" and RGBCMY. So the Velvet may be a 3chip + 1 chip design, after all.
I reported in http://www.avsforum.com/avs-vb/showthread.php?t=1140204&page=2 that my NEC HT-1100 from 2005 has a yellow primary.

"6LCD, 3*2, 2 in series for each color" This one is interesting; if the panel pairs can be gotten close enough together, they could act as single high-CR panels and eliminate the need for the relay optics.

If the first LCD has its usual transmissions, then the second LCD must have transmission 100% for all pixels except those where the first has 0%. For those the second LCD has transmission 0%. Whatever tranmissions you give to the first and second LCD, their product, at each pixel, must be the value you want.

The need for polarizers and the scatter by the LC means the series pair needs to be spaced apart and a relay lens inserted between. So this 6 LCD design requires 3 relay lenses, great trouble, bulk, and expense.

Consider LCoS first. A fourth chip can't modulate luminance or else the luminance signal would get squared. So the fourth chip needs to be at 100% at all pixels except those pixels which have R=G=B=0 from the first three chips.You lost me there. Why couldn't the 4th panel modulate luminance much like a dynamic iris does now, except in small zones or individual pixels (which would be harder)? Basically, if an area has the brightest pixel at 50% of the light power of white, the 4th panel (or 1st panel with all the others after it) could be set to 50% and then the same pixels on the other panels have their signals adjusted appropriately. Just like a good dynamic iris system, this would require modulation of the signal level to get things other than video black back about where they would be otherwise, except that being able to do it in small zones or down to the pixel level would avoid the problem that dynamic irises have where the image calls for bright pixels in one part of the image and black in another part.

--Darin

The concept can be implemented in many ways
2DLP, 1+1
4DLP, 3+1
1DLP +1LCD
4LCD, 3+1
6LCD, 3*2, 2 in series for each color
3LCOS +1LCD
4LCOS

In all these realizations except the 6 LCD, we need to be careful to recognize that the second stage is not really a luminance modulator. Most simply the second stage is monochrome, but binary: just two levels: on and off. The second stage is at full on except where the previous chips are all at at full off.

What I described as an optical near impossibility a few posts up was a 6 LCoS design with one relay lens. We should consider what possible advantages there are to 6-chip designs which apply a separate series to each of the R,G,B? Again, the second chip in the series will most simply operate as a binary switcher. It will just clean up the 0 signal from the first chip. Each of the R,G,B images will have an extra-clean 0, while the 4-chip designs accomplish a little less: their final image is extra-clean where R=G=B=0. If our eyes were better organs than they are, the 6-chip design could thereby produce some purer colors than the 4-chip design. It won't be seen. What other advantage does the 6-chip design have over the 4-chip design?

You lost me there. Why couldn't the 4th panel modulate luminance much like a dynamic iris does now, except in small zones or individual pixels (which would be harder)?

Sure, you can doctor the image if you dare. You're hesitant to apply the DI-thinking down to the pixel level, because this can screw-up any dithering the video got before the projector. But you're allowing the projector to look for "zones", things, pubic hairs in coca cola perhaps, to do its new expanded job. The projector is now the artist himself, not the old sign hanger.

You're risking horrendous artifacts and ugliness.

I concede that by making the second stage binary I was already introducing artifacts. I think the sane way to utilize two stages is with a filter wheel and the two DLP's perfectly in synch.

Again, the second chip in the series will most simply operate as a binary switcher. It will just clean up the 0 signal from the first chip.

???
I do not know why you limit the use of the extra modulation step like that since that is not what is done in HDR displays. Each step in existing designs do 8 bit per step in the series. Sim2 and Dolby are now doing this in a commercial product. It is a display with step1 LEDS and step 2 is a flat panel lcd. This unit has very powerful LEDs that makes it HDR which demands very bright whites and not just very dark blacks.
Samsung is doing this in a scaled down fashion for consumers.
The next step should be to applly this to front projection.

??? I do not know why you limit the use of the extra modulation step like that since that is not what is done in HDR displays.

I was wrong.
In a 6 LCD design (2 in series for each color) each chip can make, for example, the square root of the intended image, so the series has the intended image.
In 3+1 design, where the 4th chip is intended as a luminance modulator, what shall its level, x, be at each pixel? If we want to get r,g,b in a certain pixel in the final image, then the first three chips must be at at least r,g,b respectively. So x is constrainted to between max(r,g,b) and 1. This will be a pretty high range for most pixels, so I said it was simplest to make x=1 except where r=g=b. But it's probably better to make x = max(r,g,b). Then the 4th chip isn't binary.

First three chips have r/max(r,g,b), g/max(r,g,b), b/max(r,g,b) respectively.
Fourth chip has max(r,g,b).
Output has r,g,b.

Sure, you can doctor the image if you dare. You're hesitant to apply the DI-thinking down to the pixel level, because this can screw-up any dithering the video got before the projector. But you're allowing the projector to look for "zones", things, pubic hairs in coca cola perhaps, to do its new expanded job. The projector is now the artist himself, not the old sign hanger.It seems like you've realized that making one stage binary doesn't make sense.

I could address your post here, but not sure how much you would still stick with. For instance, your comment about the projector not being the artist himself doesn't make sense to me since what the projector is trying to do is get things where they are specified to be. Using zones and more than one stage is part of getting there when one stage can't go dark enough.

As far as zones, that is mostly because it is hard to converge things. And zones have already been done in a flat panel to good effect.
I think the sane way to utilize two stages is with a filter wheel and the two DLP's perfectly in synch.How do you plan to converge them, or would you just live from the artifacts caused by not having them converged?

--Darin

Here is an exemple of how LED LCD work. We also discussed 2 DMD in the same thread.

http://www.avsforum.com/avs-vb/showthread.php?p=11689250#post11689250

As far as zones, that is mostly because it is hard to converge things. ... How do you plan to converge them, or would you just live from the artifacts caused by not having them converged?

I don't know what you mean by "converge" in either of your points. Align? Do you think a relay lens can't carry one DLP onto another, pixel to pixel? 1:1 relay lenses are generally symmetrical and so have 0 distortion.

"The need for polarizers and the scatter by the LC means the series pair needs to be spaced apart and a relay lens inserted between."

If they're very close and/or masked between pixels it seems scatter would not be an issue.

And why would the light need to be re-polarized between panels?

I don't know what you mean by "converge" in either of your points. Align? Do you think a relay lens can't carry one DLP onto another, pixel to pixel? 1:1 relay lenses are generally symmetrical and so have 0 distortion.All it takes is for a chip to be twisted or shifted slightly, regardless of how perfect a relay lens is. There are other things involved, but in production 3 chip DLPs sure don't do perfect convergence over the whole image on average from what I've seen. Heck, I think even getting one with perfect convergence in the center of the image is a crapshoot with consumer 3 chip DLPs. They may only be off by say a third of a pixel, but even that would be a problem with a 2 chip system relying on perfect alignment from one chip to the next at the pixel level.

--Darin

All it takes is for a chip to be twisted or shifted slightly, regardless of how perfect a relay lens is. There are other things involved, but in production 3 chip DLPs sure don't do perfect convergence over the whole image on average from what I've seen. Heck, I think even getting one with perfect convergence in the center of the image is a crapshoot with consumer 3 chip DLPs. They may only be off by say a third of a pixel, but even that would be a problem with a 2 chip system relying on perfect alignment from one chip to the next at the pixel level.

--Darin

In the bright side project they use a low resolution solution to enhance the high resolution panel. Can the same be done with 2 DMD? I would think the they first DMD don't need to be perfecltly align if it's light it's not perfectly focus on the second panel.

http://www.bit-tech.net/hardware/2005/10/04/brightside_hdr_edr/1

...3 chip DLPs sure don't do perfect convergence over the whole image...

3 chip DLPs are cursed with their prisms. Prisms can introduce serious aberrations in image forming systems. Just because their surfaces are flat doesn't mean they play straight. I wouldn't blame the chip geometry before examining the prism's contribution.

"I would think the they first DMD don't need to be perfecltly align if it's light it's not perfectly focus on the second panel."

And in that case they could use a cheaper lower res DMD.

"I would think the they first DMD don't need to be perfecltly align if it's light it's not perfectly focus on the second panel."

And in that case they could use a cheaper lower res DMD.

Don't know if it would be that much cheaper. A lower resolution DMD would need another scaling circuit. The same resolution DMD would work on the same circuit.

I far from being an expert. Just my intuition.

If they're very close and/or masked between pixels it seems scatter would not be an issue. And why would the light need to be re-polarized between panels?

If you take your idea of series LCDs, without intermediate polarizers, to the limit, you reach a single LCD! What would be the advantage of splitting the LCD into one liquid crystal with half the full image voltages applied followed immediately by another liquid crystal with half the full image voltage applied?

This strand has discussed how black level is lost with DLPs. I don't know how it's lost with LCDs. From this position of ignorance I can still be pretty sure that a relay lensed series of two complete LCDs can yield a better 0 than one complete LCD. Now just suppose that imperfect linear polarizations by the front and rear sheets contributes to poor black level from a complete LCD. Then by omitting the polarizers between the series pair we haven't reduced this loss factor. By including the polarizers between the series pair we have.

In the bright side project they use a low resolution solution to enhance the high resolution panel. Can the same be done with 2 DMD?

The idea of combining a low resolution chromaticity signal with high resolution luminance signal is embodied in color subsampling (4:2:2, et al.) and is visually sound. It requires that we first separate the one dimension of luminance from the two dimensions of chromaticity. I.e., transform the RGB to something like YUV.

Because one stage in the series designs is working purely on luminance, it might be thought that the other stage is working purely on chromaticity. Not so when that other stage is RGB. There might be equal luminance information conveyed by each stage. Making one stage lower resolution than the other simply yields a compromise resolution.

See how the luminance modulation is split between the two stages in my belated example:
First three chips have r/max(r,g,b), g/max(r,g,b), b/max(r,g,b) respectively.
Fourth chip has max(r,g,b).
Output has r,g,b.

looking on page 246 table 8.1 of " Introduction to Microdisplays it looks like diffraction scattering accounts for a degradation in contrast of only 65000/1 pixel to pixel and that mirror surface scatter is not an issue. That leaves pixel to pixel edge scatter and back plane scatter where I believe backplane scatter dominates and can only be improved by improving the back plane absorption coating.

the more pixels you have the more edges you have which will scatter into the focal plane. Making the edges thinner will reduce edge scatter but will compromise the strength of the mirrors

I think the current pixel to pixel contrast ratio of DLP is around 1300/1. The problem of contrast ratio limits of DLP micromirrors has been modeled extensively both in closed form and using scattering programs like ASAP and Fred and is well understood and agrees with laser scatter experiments.

I really believe the quality of projectors is limited by the optics in front of the projectors and for DLP projectors the big difference would be the Quality of the projection lens and the assembly tooling.

the big difference would be the Quality of the projection lens.

The best lens currently on the market are the big Minoltas in some of the best projectors money can buy but unfortunately sub 2k projectors with plastic lens outperform these projectors in areas most important to all on this forum. While those lens are nice indeed they singly do nothing to increase the performance of the projectors they are used with that anyone here would be willing to pay the extra 3 to 4k.
Knowing every projector made regardless of cost leave something to be desired in other areas that most here would probably deem more import then a better lens as most Lens are already doing a passable job. Yes it would be nice to have "THE BEST LENZ" in my projector but no one visiting for a movie will see the difference but their eye will most likely pick up on any improved ANSI or increased on/off etc much easier. Of all things in demand I do not think most here would consider an improved lens high on the list
but I would not say no if it were offered. We want every ninth of improvement we can get.
Maybe some day we will have it all in one projector but then what would we have left to talk about:)

I think the current pixel to pixel contrast ratio of DLP is around 1300/1. The problem of contrast ratio limits of DLP micromirrors has been modeled extensively both in closed form and using scattering programs like ASAP and Fred and is well understood and agrees with laser scatter experiments.

I really believe the quality of projectors is limited by the optics in front of the projectors and for DLP projectors the big difference would be the Quality of the projection lens and the assembly tooling.The main place where I see DLP lagging right now (other than the Lumis) is in on/off CR, not ANSI CR and likely not MTF at either full resolution or close to full resolution. Do you believe it is the optics for DLP projectors that are limiting their on/off CRs, that lack of on/off CR isn't a disadvantage for them compared to say the RS20, or something else?

A contrast ratio pixel to pixel of 1300:1 is huge and the lenses likely are a big limiting factor there. But this is also where our eyes have less ability to see across a high contrast ratio range. It is contrast ratio between pixels that are far apart and sequential contrast ratio where I believe our eyes can generally discern higher contrast ratios. In other words, when dark is next to white it doesn't have to be too dark to fool our eyes, but when dark is separated by some distance from white either spatially or temporally it takes more CR to fool our eyes into thinking the dark stuff is black.

--Darin

Darin. Come on my friend. He obviously is not saying that the lens is causing the on/off to be lower. Given that the is a limit to what on/off a single DLP chip without some dynamic means (whether, DI, DB, led dimming yada), the biggest weakness is the lens. And I would agree.

Alan. Most of the projectors in this forum don't use plastic lenses. But they use relatively slow F stop wise lenses with very wide zoom ranges.


A better lens could improve a variety of things. More light output, higher MTF, lower CA, a bigger sweet spot for lens shift without worsening CA. Better sharpness.


Let's focus say on a Planar 8150. Its not quite as sharp as say a Marantz 11S2. or a Samsung SP-A900B. Suppose it had a better lens. The MSRP differential using a lens of the Qualia quality, the MSRP differential might be $3K with a street of course lower. Would I pay say $2500 more? You betcha.

Now lets leave the realm of single chippers. Let's take a 3 chip RS20. It uses a pretty good all glass lens. It has an on/off around 40,000 as measured by Greg R.

Where is it weak and what would I pay to buy a better one.

First, I'd like hand picked tight convergence. Same light engine, just pick the best converged ones for the high end model.

Then a lens of the Marantz or Samsung quality,

A better processing chip would be nice but that is easily addressable by an external processor.

Suppose it cost $4000 MSRP. At street, would I pay the difference? You betcha. No and, ifs, or buts. Add a switchable well implemented DI and I'd be in upper New York state heaven. Of course, that might be considered hell in Hawaii.

Let's focus say on a Planar 8150. Its not quite as sharp as say a Marantz 11S2. or a Samsung SP-A900B. Suppose it had a better lens. The MSRP differential using a lens of the Qualia quality, the MSRP differential might be $3K with a street of course lower. Would I pay say $2500 more? You betcha.

I think you'd be one of the very few to pay 20-40% more for only a better lens. Just look at (for example) the W5000 vs the W20000, there aren't many people who sprung for the better DMD at about that same cost difference.

Where is it weak and what would I pay to buy a better one.

First, I'd like hand picked tight convergence. Same light engine, just pick the best converged ones for the high end model.

Then a lens of the Marantz or Samsung quality,

A better processing chip would be nice but that is easily addressable by an external processor.

Suppose it cost $4000 MSRP. At street, would I pay the difference? You betcha. No and, ifs, or buts. Add a switchable well implemented DI and I'd be in upper New York state heaven. Of course, that might be considered hell in Hawaii.

$11.5k MSRP? Again I think very few would make that jump.

The big issue with either of these ideas is you're leaving one market and entering an entirely different, and much more limited one.

That's why it would be an upscale high end model. Plenty purchased the Marantz 11s1. If Marantz had a well executed DI like the Planar 8150 and it cost $9000 MSRP compared to the $7K MSRP of the Planar 8150, you don't think it would sell well?

JVC would sell plenty of an upscale RS20 with the things I suggested. Whether people with a budget of a street price RS20 would buy it, no. It would be at least several thousand above their budget. But people with a higher budghet would scoop it up.

It would be one thing to say I'd like it but can't afford it. Most people will poo pah the improvement saying it isn't worth it. Just like the RS2 lens was OK. The colors aren't that bad Yada Yada.

You stick with your RS20, its a fine projector but I'll enjoy the better upscale model and I'd bet that quickly would become Greg R and WSR's reference. Many would like the Lumis but its way out of their budget. But a few K more in this sport? Sign me up.

It really would make sense for JVC to have a high lumen projector: something to compete with the 3 chips dlps.

If JVC can keep contrast at RS20 levels but have somewhere near 2000 lumens, I think they could steal some of the 3 chip DLP market and they could charge a lot more for the product. I don't know how something like this would be received. It would, no doubt, have the kind of lens options that Mark is calling for.

An RS20 with an expensive lens, a Xenon lamp and an external VP? Not interested.

A significantly higher lumen model would be an expensive investment for JVC. A chassis redesign would be required. Expensive. Adding a lens mount, hand picked convergence, a bigger diameter lens (would increase brightness obviously without adding more heat), higher MTF, a better processing chip, these would be doable in the added $3500 more MSRP range.

That's why it would be an upscale high end model. Plenty purchased the Marantz 11s1. If Marantz had a well executed DI like the Planar 8150 and it cost $9000 MSRP compared to the $7K MSRP of the Planar 8150, you don't think it would sell well?

I think it would sell not nearly as much as the Planar. That's the point, you made it sound like almost everyone intested in a $7K Planar would be happy to pay $2k more for the "super lens" version. I really, really doubt that's the case. At the Lumis price point, probably, but not at the Planar point.

That is, I think, what Alan was getting at, the difference between a "good" and a "bad" lens just isn't worth the price difference to most people.

No doubt Planar and JVC could sell "upscale" machines with awesome lenses and cherry picked light engines, but most people in the market for those I think would pocket the cost difference or spend it elsewhere in their HT, like for a good VP which would probably make much more difference than the lens would.

Look at it this way, if a lens is a 1% improvement, there are lots of other things that cost less that provide a 5% or even 10% improvement.

JVC would sell plenty of an upscale RS20 with the things I suggested. Whether people with a budget of a street price RS20 would buy it, no. It would be at least several thousand above their budget. But people with a higher budghet would scoop it up.

Which is exactly my point. Yes it would sell, but not nearly like an RS20.

It would be one thing to say I'd like it but can't afford it. Most people will poo pah the improvement saying it isn't worth it. Just like the RS2 lens was OK. The colors aren't that bad Yada Yada.

I'm not saying anything about whether it's "worth it", just that contrary to the way your response to Alan read, people wouldn't be flocking the streets for it.

You stick with your RS20, its a fine projector but I'll enjoy the better upscale model and I'd bet that quickly would become Greg R and WSR's reference. Many would like the Lumis but its way out of their budget. But a few K more in this sport? Sign me up.

I've got a DLP (which I'm looking to upgrade sometime soon-ish), the RS20's on the list, but not necessarilly the top, so is the Planar, but your fictitious machines most certainly are out of my budget, but you should enjoy your upscale machines if you can afford them, I know I would. I think I read your post differently than you intended. It reads a lot like the "I would, wouldn't everybody!?" posts (especially in the context of responding to Alan) you see all over and that's how I took it.

"He obviously is not saying that the lens is causing the on/off to be lower."

It sounded to me like that's exactly what he said.

"Given that the is a limit to what on/off a single DLP chip without some dynamic means (whether, DI, DB, led dimming yada), the biggest weakness is the lens. And I would agree."

Lenses have no effect on on/off CR.

Lots more people buy $2500 projectors than projectors for RS20 street, A hell of a lot more. But the folks here at the above $3000 forum shelled out for the 20. Believe it would be only a 1% improvement? How much lens improvement was there from the RS2 to the RS20. That new lens didn't cost JVC any more. Sharper my boy costs more and plenty want sharp. All else being equal, sharper sells. Every one can see it. The JVC lens is not super sharp and coupled with the projectors average misconvergence, a tightly converged and sharp lens model would make JVC plenty of mpney.

Many many many bought Pioneers rebadged RS2 for $3K blowout. Cheap sells, People compromise quality for cheap particularly in today's economy. But plenty still bought RS20s even when the Pioneer blowout happened. The RS20 is not that much better than the 20? What would you say? By what percent. Say the new JVC is 20% better in PQ, would you pay say 35% to 40% more? It becomes an issue of how important is better PQ to you and whether it can be afforded comfortably. A better processor is needed to fix a flaw in the RS20. $30 more dollars spent by JVC for a better chip would obviate much of the need for a better processor.

You read it that way. From his posts and knowledge I know he didn't mean it that way. A single chipper has the potential to be incredibly sharp and have almost 0 CA, what is needed here for that is a better lens. That's the way I read it, Perhaps he will chime in and clarify.

It really would make sense for JVC to have a high lumen projector: something to compete with the 3 chips dlps.

An interesting question LG.

They already have that with 4k unit, for commercial use. Meridian use that as the basis of the 810. I auditioned that machine for my new room and found it to be very disappointing, as have a number of other AVS members.

If JVC can keep contrast at RS20 levels but have somewhere near 2000 lumens, I think they could steal some of the 3 chip DLP market and they could charge a lot more for the product. I don't know how something like this would be received. It would, no doubt, have the kind of lens options that Mark is calling for.

I don't think it would be received particularly well at all, if it were aiming at the high end sector. It would need to attend to a number of things. That end of the market has some serious requirements that need to be met. They would need to improve the following areas...ANSI, Sharpness, Motion handling, Uniformity, Pixel noise. I think JVC will look at the mid level sector very soon. There is still work to be done before the high end is attempted. Personally, I think its something that JVC will look at.

An RS20 with an expensive lens, a Xenon lamp and an external VP? Not interested.

An expensive lens will not address most of the underlying engine issues. A constant apperture lens would be good,as would splitting the zoom range. If ALL the issues above were addressed, I would consider it. Unfortunately they have been beaten to the punch by the Lumis.

for DLP projectors the big difference would be the Quality of the projection lens and the assembly tooling.

As with a number of others above, I need to say you are way off base.

I agree with Mlang. I do agree that it wouldn`t be a highest endm but something above the 20 whatever that level you want to call it.

As good as it has to be? Hardly. it could be a lot sharper and have a much bigger sweet spot for all that use lens shift I have no clue what its MTF is but i bet it could be a lot higher with overal PQ improvements. Mlang is the optical expert here. Although I respect you CM, I think Mlang knows a lot more about lenses then you do. and me for that matter. But that doesn`t lessen my respect for you CM or your knowledge and expertise.

That's why it would be an upscale high end model. Plenty purchased the Marantz 11s1. If Marantz had a well executed DI like the Planar 8150 and it cost $9000 MSRP compared to the $7K MSRP of the Planar 8150, you don't think it would sell well?

JVC would sell plenty of an upscale RS20 with the things I suggested. Whether people with a budget of a street price RS20 would buy it, no. It would be at least several thousand above their budget. But people with a higher budghet would scoop it up.

It would be one thing to say I'd like it but can't afford it. Most people will poo pah the improvement saying it isn't worth it. Just like the RS2 lens was OK. The colors aren't that bad Yada Yada.

You stick with your RS20, its a fine projector but I'll enjoy the better upscale model and I'd bet that quickly would become Greg R and WSR's reference. Many would like the Lumis but its way out of their budget. But a few K more in this sport? Sign me up.

I would have to agree. For larger screens, you're kind of stuck with either 3-chip DLP, or going balls to the wall with the 4K JVC. A really bright LCOS machine to compete with a Titan for instance (in terms of light output) might be a smart move, with lens options, for the high-end market. But the problem is the economy, so it makes sense that JVC didn't make a big push in that direction over the last year. Over the nest year or so though, I think a product like that would make sense.

I agree with Mlang. I do agree that it wouldn`t be a highest endm but something above the 20 whatever that level you want to call it.

As good as it has to be? Hardly. it could be a lot sharper and have a much bigger sweet spot for all that use lens shift I have no clue what its MTF is but i bet it could be a lot higher with overal PQ improvements. Mlang is the optical expert here. Although I respect you CM, I think Mlang knows a lot more about lenses then you do. and me for that matter. But that doesn`t lessen my respect for you CM or your knowledge and expertise.

Mark, I meant that the lens is as good as it needs to be for its current market. I deleted the comment to avoid misunderstanding. Also, the image softness is due to the underlying architecture, not simply the optics. This can be seen on the JVC 4k (and the 810) and, similarly on the Sony 4k units, both of which use vastly superior optics.

I agree that there is a good gap between $20k and $40k that currently needs exploiting.....with the right product. Unfortunately, for the moment at least, there is a reason for that gap.

Mlang is also the expert in fabricating bogus test reports, and has an extensive history of posting absolute garbage with no basis in fact whatsoever.

CM. Thanks. You are a mench and a scholar.

I thought you might come back that there are elements besides the lens in the JVC that might be weaker links.

Of course, the JVC is not a single chip DLP and that was the focus of Mlangs comment re lensesm that that is the weak point of many projectors in the single chip DLP category.

Moving on to the 3 dila chips of the JVC, there are of course other weaknesses compared to the real high end machines.

But some in ways it betters them. You pointed out some of those weaknesses in your self deleted comments. I would agree for its street price point it is well balanced. It clearly could be better for more money though and I for one would like to see it.

Yes it would be nice to have "THE BEST LENZ" in my projector but no one visiting for a movie will see the difference but their eye will most likely pick up on any improved ANSI or increased on/off etc much easier.

Contrast, generally ANSI contrast, is exactly why the discussion shifted to lenses. When the bugs are worked out of the "light engine" there is still the flarey projection lens to contend with. Even perfect air-to-glass surfaces, with excellent multicoatings, reflect. In a complex lens the reflections have a fair probability of being re-reflected back toward the screen. The market's demand for zoom lenses means greater complexity and reduced ANSI contrast. Projection purists should choose non-zoom, non-wide angle lenses with the simplest construction consistent with high sharpness.

Imperfect air-to-glass surfaces, and coatings, also scatter. "Laser quality" glass surfaces cost much more and scatter much less. It's a feat to make a glass surface which doesn't scatter at least 0.1% of the light incident upon it. 1% is more typical. This limits ANSI contrast as does multiple reflection. Volume scatter due to glass impurity is another consideration.

Lens sharpness is contrast at middle to high spatial frequencies. ANSI contrast pertains to the near-zero spatial frequencies. The two kinds of contrast are independent and BEST LENZ would excel at both.

Projection purists should choose non-zoom, non-wide angle lenses with the simplest construction consistent with high sharpness.
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Isn't it more of the lens size that affects image quality? The bigger the lens with the same MTF, with the same number of line pairs means sharper image? The lenses on my projector are over 5" wide for each of the three lenses. Also, mine have a super short throw of 1.2x. Short throw means wide angle? Yet the lenses themselves make a very sharp image.

Another thing, why don't these super expensive digitals have a lens that does: center, corner and edge focus control, along with Schiemflug ( lens tilt )? For how much they cost, you should get better focus controls than a single ring focus!

You obviously are talking CRT lenses. There is a big difference here. The size of the image being sent through the lens. Nine inch CRT tubes require a very wide lens. It is critical how the tube face lines up accross the back surface of the lens. These images from a CRT are not as sharp as the best digitals, even digitals in the $7.5K MSRP class, Looking through the lens back at the chip or chipsm only a small portion of the lens is used. edge focus just isn`t required in this case. However getting the front surface of the lenses parallel to the the screen is. The very best digitals, those in the plus $60k class do have Schiemflug adjustments. This is the equivalent I think to edge focus.

CRTs have very low ANSI CR but very high on\off CR.

Well, if the technology in my Lumis can migrate down into lower priced DLP's, contrast won't be a problem with DLP's anymore. After watching Dark City tonite, all I can say is WOW !!

Well, if the technology in my Lumis can migrate down into lower priced DLP's, contrast won't be a problem with DLP's anymore. After watching Dark City tonite, all I can say is WOW !!

It is interesting you say this because I didn't get the impression from comments with Darin that the Lumis had visible contrast improvements over the Planar.

Any thoughts on the is Alan? Darin?

Quote:
Originally Posted by Craig Peer
Well, if the technology in my Lumis can migrate down into lower priced DLP's, contrast won't be a problem with DLP's anymore. After watching Dark City tonite, all I can say is WOW !!
It is interesting you say this because I didn't get the impression from comments with Darin that the Lumis had visible contrast improvements over the Planar.

Any thoughts on the is Alan? Darin?
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I can't say since I haven't seen the Planar. However, at least 2 people on the 20k+ forum directly compared the Lumis with the RS20, with the Lumis being superior contrast wise ( and in other areas, although those may be due to the 3 chip DLP design ).

Interesting. I've heard the contrast was good but I'd be surprised if the dynamic system could truly match the RS20 with very low APL sequences. Mixed scenes is believable though. Darin and I did some comparisons with the Planar and the RS20 and found the Planar to be better in areas as well depending on the content, but the RS20 still pulled ahead with really low APL scenes or total blackouts.

The dynamic iris system on the Planar is one of the best I've seen but I would love to compare it to Sim2's.

I can't say since I haven't seen the Planar. However, at least 2 people on the 20k+ forum directly compared the Lumis with the RS20, with the Lumis being superior contrast wise ( and in other areas, although those may be due to the 3 chip DLP design ).

Craig,

Myself, Alan Gouger and Wolfgang all compared them directly and simultaneously. I believe Free did as well. We all reported that the Lumis clearly had the better black level and low APL performance. There are also a number of other RS20 owners who have bought a Lumis, with similar results.

Its certainly not fair to compare the 2 in terms of overall performance or PQ, considering the price difference. We were only referencing the low APL, as the RS20 had set a marker in that area. That said, The PQ differential is, understandably, very significant.

Wolfgang posted shots of black screens, and I have done the same.

There is far more to the Lumis performance than just a DI. That, and the above info, has been well reported on the high end forum.

Hope this helps.

Coldmachine pretty much said it all !!!

Craig, as I posted elsewhere, get the Renaissance BD....trust me. It kills most PJs, and is tailor made to demonstrate the strengths of the Lumis.

I have the Renaissance BD. DLPs typically do better with this disc than the JVC, though the difference has never been night or day. The Marantz showed better blacks than the JVC with this one but I don't know if I've looked at it with the Planar. Obviously the strong ANSI of the DLPs shines here.

Thanks for the comments coldmachine!

The main place where I see DLP lagging right now (other than the Lumis) is in on/off CR, not ANSI CR and likely not MTF at either full resolution or close to full resolution. Do you believe it is the optics for DLP projectors that are limiting their on/off CRs, that lack of on/off CR isn't a disadvantage for them compared to say the RS20, or something else?

A contrast ratio pixel to pixel of 1300:1 is huge and the lenses likely are a big limiting factor there. But this is also where our eyes have less ability to see across a high contrast ratio range. It is contrast ratio between pixels that are far apart and sequential contrast ratio where I believe our eyes can generally discern higher contrast ratios. In other words, when dark is next to white it doesn't have to be too dark to fool our eyes, but when dark is separated by some distance from white either spatially or temporally it takes more CR to fool our eyes into thinking the dark stuff is black.

--Darin

The discussion is about DLP projectors. the on/off on A DLP is limited by the Edge scatter and the reflections from the back plane but that is true for all DLP projectors but basically if you want to improve the on/off contrast improve the the anti reflection coating on the back plane

But if you are using the same chip and everybody buys from the same manufacturer the biggest improvement is going to be from the optics and probably the projection lens which would include coatings , surface scratch and dig and adding more aspheric elements to improve the resolution.

your perception of sharpness is how well the projector projects images at higher spatial frequencies and that is severely limited by the lens. We are not talking 300/1 or 1200/1 we are talking going from 2/1 at 20lpm to 10:1 with a superb lens and you will definitely see that

Given any particular DLP chip your instantaneous on/off contrast is pretty much set in stone assuming you don't make any obvious mistakes in the design which you will not if you follow TIs guidance. So the real limitation on performance are the optics for a one DLP chip

Alan's comments about plastic lenses do not make any sense to me. plastic lenses are great for cameras but because of internal striations and surface roughness they should never be used for lamp based digital projectors because they will scatter too much light into the focal plane. Plastic lenses are used in CRT projectors because of the large focal plane so the irradiance on any one element is small

On/off contrast and ANSI contrast are extremely important but are limited by the technology you chose. Some people naively think you can jack up the gamma to improve contrast but you can't without distorting the colors

Interesting if you replace the wire grid polarizers in RS20 with calcite polarizers and improve the projector lens you could probably get an on/off contrast of over 100,000/1 with ANSI contrast of over 2000/1. It would be expensive but it would be sweet. Maybe I will buy an RS20 and modify it if I don't get the money I am trying to raise for my next adventure into the insane world of a start up.

to summarize: the limits of DLP chip's on/off contrast are well known , well categorized and well understood. Put a better coating on the black plane and on/off contrast is dramatically improved. You want real improvement Wait for Darkchip 5

Great post Mlang. What's a calcite polarizer? One for each chip? Where would it be in the optical path? How much do these cost in small and large quantities? Have you heard anything about a DC5 chip?

My guess is there will be an upscale RS20 from JVC announced at Cedia and available by late 4th Q. Hopefully this will have better lenses with less wide zoom ranges. Before I would mod anything, the convergence would have to close to spot on. Hopefully the new model will have a tighter convergence spec. Then all that might be needed is these calcite polarizers. Eagerly awaiting your response.

Looking on the net, I'd guess about $500 to $600 each. Then install labor. I modded my CRT for a lot more than that many times.

Interesting if you replace the wire grid polarizers in RS20 with calcite polarizers and improve the projector lens you could probably get an on/off contrast of over 100,000/1 with ANSI contrast of over 2000/1. It would be expensive but it would be sweet. Maybe I will buy an RS20 and modify it if I don't get the money I am trying to raise for my next adventure into the insane world of a start up.

to summarize: the limits of DLP chip's on/off contrast are well known , well categorized and well understood. Put a better coating on the black plane and on/off contrast is dramatically improved. You want real improvement Wait for Darkchip 5

How do these calcite polarizers work? If black levels and on/off are fixed with a digital, my two other complaints are non-overlapping convergence like on CRT and I've yet to meet a digital which can beat my color corrected SMPTE-C lenses. So I'm hoping this calcite also works on a DLP? It'd be sweet to get a used Christie or Barco D-cinema for under $20k and get it to CRT-like black level and on/off.

I'm really screwed. I can't stand noisier CRT projectors than my Dwin, so I'm stuck at 1080i max, and you can't do the CRT-walk with a digital, go look it up on Curt Palme's forum.

"So I'm hoping this calcite also works on a DLP?"

DLP's don't have polarizers.

"So I'm hoping this calcite also works on a DLP?"

DLP's don't have polarizers.

Damn! Cause I've seen JVC's D-ILA, don't like it. No matter what you do, can't get correct colors, besides using a Radiance. Another, the dithering, ghosting, etc, is horrid on the D-ILA :( SXRD I like, but Sony doesn't seem to care about winning the contrast war. SXRD has great motion like DLP but without the rainbows. Once I finally replace my CRT, it'll have to be something with the quality of a D-cinema projector but also the good black level and on/off of my CRT too. Guess I'll be waiting a while. Good thing a CRT projector isn't like a digital and dies in a month, huh? :D

Maybe these calcite polarizers could be put on the upcoming VW90, but would you still get 100,000:1+ on/off like mlang predicts with the RS20?

Looking at a diagram for a Dila light engine using wire grid polarizes, there are apparently wire polarizing beam splitters and polarizers. Is that it. Just replace the all in one polarizer splitter with another type of polarizer beam splitter. Its not apparent to me iwhether the beam splitter polarizer is one part in front of each chip or several parts.

The discussion is about DLP projectors. the on/off on A DLP is limited by the Edge scatter and the reflections from the back plane but that is true for all DLP projectors but basically if you want to improve the on/off contrast improve the the anti reflection coating on the back plane

My original post was based on a mistake. A 10 micron mirror does diffract a lot of the light it is supposed to reflect, but I ignored the effect of the mirror being square. For a square the diffraction is mostly in two orthogonal directions, so arranging the projector so the lens at the 45 deg direction (wrt the mirror orientation) means very little diffracted light gets into the lens.

Since his post #10, mlang has emphasized the contribution of the back surface. Light that slips through the crack between two adjacent mirrors reaches the slightly reflective back surface where some of it reflects back. I'm puzzled that this is a significant contributor because the space behind the mirrors is actually a good light trap. Only a small fraction of what reflects back off the back surface finds the crack again. Most of it finds the rear of the mirror or other stuff between the mirror and the back surface. If all of that is decently blackened then the light trapping works. Furthermore, since the cracks between adjacent mirrors are extremely narrow, whatever emerges from a crack is strongly diffracted, so only a small fraction can find the lens.

mlang's second factor, edge scatter, is more convincing. For the benefit of the non-optics people, this is non-directional scatter from rough edges not to be confused with "edge diffraction" which is an alternate description of the diffraction by the square shape and is directional. Observing the array from the viewpoint of the lens adjacent edges are too near to optically resolve, so it is probably impossible to observationally distinguish between the first factor (return from the back plane) and the factor of edge scatter. The crack between mirrors might be 1 micron wide but it is (or should be) cavernously dark. The rough margin of each mirror might be just 0.01 micron wide, but it is highly reflective and thus a much greater contributor to stray light. The arithmetic is tough for TI. Rough margins of 0.01 micron amount to 0.4% of the area of the mirror. If the scatter is uniform, 1/32 of it finds an f/2 lens. This makes 1/8000 of the light falling on the mirror reach the lens even when the mirror is tilted so as to make none of the light it reach the lens.

A 10 micron mirror does diffract a lot of the light it is supposed to reflect, but I ignored the effect of the mirror being square.

What if you curved each mirror? Would that increase contrast on/off as much as adding a second panel?

They are polarizers made from birefringent material meaning that when linear polarized light passes through one axis it travels at a different speed than when it passes through the axis that is perpendicular to it. its a natural mined material and by cutting the crystal and combing them you can typically get extinction ratios of 100,000 to 1 either in what they call a glan taylor , glan thompson glan laser configuration. the one off price for the apertures you would need is probably around 1000 dollars each

When I looked at the pixel to pixel contrast ratios of Lcos devices in the literature I surprised to see that the fundamental contrast ratio of the newer devices was 2000/1
Obviously with an ANSI contrast ratio of only 300/1 something else is going on and I suspect that scattering from the wire grid beamsplitters which you can't filter is limiting that contrast. I have not done the scatter analysis myself but I know who has

I may be easier to add a fourth lower resolution panel to increase the ANSI contrast.

The discussion is about DLP projectors.My fault. I took it as between the technologies too.
... so only a small fraction can find the lens.And it isn't just finding the lens. It is finding its way through to the other side of the lens, which often means making its way through an iris. As we've seen, a closed down iris can improve the on/off CR of the light on the other side.

I think I've mentioned this before, but I wish I knew where the picture was I saw from years ago from TI that showed a mirror under what I think was an electron microscope. My memory is that it clearly showed that there were 5 points that light was coming from (when there shouldn't have been any) which completely swamped the light from any other points. Those 5 points were the dimple in the center of the mirror and the 4 corners. I don't recall seeing any significant amount of light coming from around the mirror, but I'm also not sure of how the test was done. Of course the light from behind the mirrors could bounce to the sides and not show up in an image like this, yet have some of it make its way to the lens and then through an iris when in a projector.

--Darin

Damn! Cause I've seen JVC's D-ILA, don't like it. No matter what you do, can't get correct colors ...I'm not sure if you know about the CMS fix for the JVC RS20, but doesn't seem like many complaints about getting correct colors out of it after that.

--Darin

I'm not sure if you know about the CMS fix for the JVC RS20, but doesn't seem like many complaints about getting correct colors out of it after that.

--Darin

I thought there were still bugs with the new firmware's CMS?

My understanding was that if you get hue correct for red, green and blue, then the saturation for magenta, cyan and yellow aren't a proper mix of the primaries? Then if you're lucky to get a compromise for those, you still have to work for not getting either too much or too little value without changing what you already did?

I also heard many comments from former CRT owners that dithering and other motion artifacts are more on the RS20? I know Joerod said the contrast and black level was way better than his VW200 but colors and refresh response were not anywhere close to his VW200, which has been described as a higher black level version of a CRT by him and Alan. Which is why Joe sold his RS20 and got a brand new VW200. Joe has the bling, yet chose the VW200, that says something....

I'm thinking I'd love something like the VW200 if only its black level and contrast came close to a CRT.

My original post was based on a mistake. A 10 micron mirror does diffract a lot of the light it is supposed to reflect, but I ignored the effect of the mirror being square. For a square the diffraction is mostly in two orthogonal directions, so arranging the projector so the lens at the 45 deg direction (wrt the mirror orientation) means very little diffracted light gets into the lens.

Since his post #10, mlang has emphasized the contribution of the back surface. Light that slips through the crack between two adjacent mirrors reaches the slightly reflective back surface where some of it reflects back. I'm puzzled that this is a significant contributor because the space behind the mirrors is actually a good light trap. Only a small fraction of what reflects back off the back surface finds the crack again. Most of it finds the rear of the mirror or other stuff between the mirror and the back surface. If all of that is decently blackened then the light trapping works. Furthermore, since the cracks between adjacent mirrors are extremely narrow, whatever emerges from a crack is strongly diffracted, so only a small fraction can find the lens.

mlang's second factor, edge scatter, is more convincing. For the benefit of the non-optics people, this is non-directional scatter from rough edges not to be confused with "edge diffraction" which is an alternate description of the diffraction by the square shape and is directional. Observing the array from the viewpoint of the lens adjacent edges are too near to optically resolve, so it is probably impossible to observationally distinguish between the first factor (return from the back plane) and the factor of edge scatter. The crack between mirrors might be 1 micron wide but it is (or should be) cavernously dark. The rough margin of each mirror might be just 0.01 micron wide, but it is highly reflective and thus a much greater contributor to stray light. The arithmetic is tough for TI. Rough margins of 0.01 micron amount to 0.4% of the area of the mirror. If the scatter is uniform, 1/32 of it finds an f/2 lens. This makes 1/8000 of the light falling on the mirror reach the lens even when the mirror is tilted so as to make none of the light it reach the lens.

I have not read the literature directly. What I am quoting from is the book Micro display devices which references some Ti literature. It could be that edge scatter predominates. One explanation may be that the mirror when it is on, is at +12 degrees and when it is off it is at -12 degrees so there may be more back plane exposed. I do know that theses devices have been modeled precisely using ASAP, a program which models multiple scatter whether propagated by diffraction or by simple geometrical scattering. The models have been verified by laser scattering measurements.

the yoke structure is around 2 microns square and I was considering that as part of the back plane and it is in the center of the mirror

"Laser measurements have shown mirror surface scattering is not significant in degrading CR" p246 Introduction to Microdisplays

I thought there were still bugs with the new firmware's CMS?

My understanding was that if you get hue correct for red, green and blue, then the saturation for magenta, cyan and yellow aren't a proper mix of the primaries? Then if you're lucky to get a compromise for those, you still have to work for not getting either too much or too little value without changing what you already did?There could still be some things like that I wasn't aware of (I haven't really kept up on it recently), but my guess is that those things would be fairly small compared to most other projectors out there, including CRTs. Try getting REC.709 primaries and secondaries with a CRT and correct gamma for all 3 colors (including blue) and I would expect most would run into real problems. And then projectors without CMSs where people may not complain that they can't get things perfect as far as primaries and secondaries because the projector doesn't have the capability anyway. Put another way, as far as hitting the primaries and secondaries with correct gamma I would guess that the RS20 is at or very near the top right now.
I also heard many comments from former CRT owners that dithering and other motion artifacts are more on the RS20?There are definitely some motion artifacts. You may have seem some pictures of banding or contouring during motion that shows up.
I know Joerod said the contrast and black level was way better than his VW200 but colors and refresh response were not anywhere close to his VW200, which has been described as a higher black level version of a CRT by him and Alan. Which is why Joe sold his RS20 and got a brand new VW200. Joe has the bling, yet chose the VW200, that says something....Could be different strokes for different folks too. I have no doubt Greg Rogers could get a VW200 no problem (Sony might even loan one for some time) and went with the RS20. Different people may be susceptible to different things and with the motion issues, other than the contouring with the RS20, I don't think we have gotten to the bottom of the issues. High speed pictures with the RS20 show basically no blurring within the images that I can see, but that doesn't mean that the way they do things couldn't cause blurring in some people's eyes (or in everybody's, but to different degrees) or that there might not be issues down in the very fine details (pixel level) that I wasn't able to pick up with the high speed videos.
I'm thinking I'd love something like the VW200 if only its black level and contrast came close to a CRT.I'm on the lookout for a new Sony model at CEDIA in September and you may want to do the same. Maybe a VW90 or VW300. Could be a contender. I'm also looking out for anything JVC announces along with others, but figure JVC and Sony are at the top of my list for most likely models that I will buy near the end of the year.

--Darin

"Laser measurements have shown mirror surface scattering is not significant in degrading CR" p246 Introduction to MicrodisplaysI haven't read that, but if it is talking about the flat part of the surface then it very well could go along with what I read in the past about the dimple and the 4 corners being their biggest problem areas. I know that in the past TI has talked about addressing things with the dimple as one thing they improved when going from one version of their chips to another.

--Darin

My fault. I took it as between the technologies too.
And it isn't just finding the lens. It is finding its way through to the other side of the lens, which often means making its way through an iris. As we've seen, a closed down iris can improve the on/off CR of the light on the other side.

I think I've mentioned this before, but I wish I knew where the picture was I saw from years ago from TI that showed a mirror under what I think was an electron microscope. My memory is that it clearly showed that there were 5 points that light was coming from (when there shouldn't have been any) which completely swamped the light from any other points. Those 5 points were the dimple in the center of the mirror and the 4 corners. I don't recall seeing any significant amount of light coming from around the mirror, but I'm also not sure of how the test was done. Of course the light from behind the mirrors could bounce to the sides and not show up in an image like this, yet have some of it make its way to the lens and then through an iris when in a projector.

--Darin

Well there's a bunch of cool pictures here, but none like you describe:
http://www.optics.rochester.edu/workgroups/cml/opt307/spr05/john/

Well there's a bunch of cool pictures here, but none like you describe:
http://www.optics.rochester.edu/workgroups/cml/opt307/spr05/john/Thanks. I also searched around with Google and didn't find the kind of picture that I recall. This was probably back in the days of the HD1 or HD2 chips (around the time TI went from 10 degree mirrors to 12 degree mirrors).

In case anybody is interested, one conclusion that I came to when modifying my Optoma H79 years ago is that not all the mirrors face the same direction (at least not perfectly). I was experimenting with different iris configurations and at one point thought that I had multiple dead pixels. After some investigation I found that if I closed the iris down tightly there were pixels that would basically look dead or close to it. My memory is maybe 10 pixels or so spread around. I thought about it a little bit and decided that the most likely explanation is that those mirrors didn't quite face the direction they were supposed to for on. But since the lenses job is to focus the DMD chip on the screen, it really doesn't make much difference normally. The light from those mirrors just takes a different path through the lens as long as they aren't so far off that the light doesn't make it to the lens. But when I closed the iris down too far some of those paths were blocked off, so the pixels looked like they were stuck off.

--Darin

And it isn't just finding the lens. It is finding its way through to the other side of the lens, which often means making its way through an iris. As we've seen, a closed down iris can improve the on/off CR of the light on the other side.

In general, closing down the iris removes the same fraction of desired light as undesired light, so it doesn't help the CR. You found in your projector that the desired light was particularly concentrated, allowing you a stop-down method.

the picture ... from TI that showed a mirror under what I think was an electron microscope. My memory is that it clearly showed that there were 5 points that light was coming from (when there shouldn't have been any) which completely swamped the light from any other points. ...the dimple in the center of the mirror and the 4 corners.

The picture couldn't be from an electron microscope or it wouldn't have shown where light was coming from. Both the diffraction and the scatter are completely different for electrons and for light.

The dimple is terrible. The scatter from the corners might also be due to surface distortion. Alternately they might be due to what mlang46 is calling "edge scatter" which happens to increase toward the corners.

There's another possibility, conceptually at least, that the place where the stray light appears to come from isn't the place where it really comes from.

In case anybody is interested, one conclusion that I came to when modifying my Optoma H79 years ago is that not all the mirrors face the same direction (at least not perfectly).

I'm interested. We're designing an instrument for a non-imaging purpose and thinking of using a TI chip, in which case I'd need to learn all its quirks.

In general, closing down the iris removes the same fraction of desired light as undesired light, so it doesn't help the CR. You found in your projector that the desired light was particularly concentrated, allowing you a stop-down method.

Maybe not projectors in general, but it is for DLPs. Darin's Optoma, the Sharp Z20000, my W5000, the IN82 all are known to show a measurable and significant increase in CR by closing down the manual iris.

In general, closing down the iris removes the same fraction of desired light as undesired light ...Only once you get down to basically the point that the "white" light is uniform compared to the "black" light so that closing it further blocks them in pretty much equal proportions. With DLPs this tends to be an iris that is somewhat closed down. And as I've explained before, 2 irises (one before the DMD in order to get the "white" in the lens down) are really the key to getting the best CR.
You found in your projector that the desired light was particularly concentrated, allowing you a stop-down method.And with DLPs this has been shown to be the case with multiple projectors. But in my case I was also controlling that concentration to some degree with the iris before the DMD (like Sharp and Marantz projectors also support).

Anyway, the point was about light bouncing from underneath the mirrors. In that case, if the lens is shut down to some degree at some point (an iris), then that "bad" light needs to make it through the lens and to the screen in order to hurt CR. By closing an iris before the DMD there will be less light bouncing behind the mirror and making it to the lens. Then by shaping an iris within the lens to match the one before the DMD pretty well, most of the white light that goes through the first iris will still make it through the 2nd iris, but the more random light from reflections will have less chance of making it through the iris in the lens because of the decreased area.
The picture couldn't be from an electron microscope or it wouldn't have shown where light was coming from. Good point. I hadn't thought about that.
The dimple is terrible.It was pretty bad, but TI has been working on smoothing it out and I don't know how much of it they have addressed.
There's another possibility, conceptually at least, that the place where the stray light appears to come from isn't the place where it really comes from.My memory is that the information came from TI in trying to figure out where the light was coming from so that they would know where to concentrate their efforts, so I figure they would have taken some steps to try to make sure that they were able to determine where the light was coming from.

--Darin

So we have basically meaning the same thing, bad light, undesired light, random light, and stray light. I think the best term would be stray light.

"...This makes 1/8000 of the light falling on the mirror reach the lens even when the mirror is tilted so as to make none of the light it reach the lens."

If I'm understanding you correctly, you're saying that the max on/off CR possible is 8000:1.

I guess that's in the ballpark of the best native DLP on/off CR.

"...This makes 1/8000 of the light falling on the mirror reach the lens even when the mirror is tilted so as to make none of the light it reach the lens."

If I'm understanding you correctly, you're saying that the max on/off CR possible is 8000:1.

I guess that's in the ballpark of the best native DLP on/off CR.

It's more like 9000:1.

"...This makes 1/8000 of the light falling on the mirror reach the lens even when the mirror is tilted so as to make none of the light it reach the lens."

If I'm understanding you correctly, you're saying that the max on/off CR possible is 8000:1.

It's me you're quoting, and no I'm not saying that the max on/off CR possible is 8000:1. It was a rough calculation based on an assumption that the outermost 0.01 microns of every mirror is a perfect scatterer. The dimension 0.01 microns is purely hypothetical. It was a calculation to show the likely relevance of "edge scatter" as mlang46 suggested.

OK, thanks.

No I don't and have not looked into more vector based EM Calculations and I am not sure if ASAP which was used to model the scattering form the DLP chips includes that type of calculation.

I haven't read that, but if it is talking about the flat part of the surface then it very well could go along with what I read in the past about the dimple and the 4 corners being their biggest problem areas. I know that in the past TI has talked about addressing things with the dimple as one thing they improved when going from one version of their chips to another.

--Darin

the article was as you said talking about the flat part of the surface. Reducing the dimple which is where the mirror connects to the lever arm has improved the/off contrast dramatically in the past but is now at its limit due to structural considerations.

I think that the brilliant engineers at TI have pretty much improved this technology to the point that further improvements are going to be incremental.

A more interesting discussion now is given the technology we have available where should development efforts be directed which will give the greatest improvements toward the ideal. software ,new color space ,better optical design better light sources , fourth panel, higher resolution, higher CR ect. The Ideal I am setting is that when you look at your projection screen you can not distinguish it from the same scene you would observe while looking out a window with the same dimensions and same brightness levels.

Could be different strokes for different folks too. I have no doubt Greg Rogers could get a VW200 no problem (Sony might even loan one for some time) and went with the RS20.I had a VW200 for months.

I had a VW200 for months.


When is the review coming?

When is the review coming?I'll wait for the next Sony projector.

I'll wait for the next Sony projector.

Any reason in particular? How about 50 words or less?

Any reason in particular? How about 50 words or less?

It's called socialist corporate capitalism. If there aren't enough people to buy something, companies, corporations and individuals will become apathetic towards supplying a good or service. Even though companies like Ferarri and Lamborghini sell a few for lots, it's a selective market. But I guess the VW200 is too selective? The TV market is something like 100 million sets a year, with total HT projectors being 600,000 according to another thread. With only a fraction of that being high end. Look at how many more sub $3,000 projectors are sold. You should therefore be lucky he gives us the privilege of reviewing any at all. Greg should just stick to the bottom line and only review LCDs since that'd give the most sales. With the way the economy is heading, I won't be surprised if the, "you can get it in any color you want as long as it's black," model doesn't make a comeback.

Lawguy, if you read between the lines of what Greg's policy about what he *does* review, which he repeated within the last week or so, you'll have your answer.

Unless there's some truth in what troglobite said, if you can figure out what that is.

Troglo whatever is way off base. He has absolutely no clue as to why greg did not review it.

I know the reason having discussed it with Greg but I am not a liberty to disclose the reasons. Greg is a good person, a honest reviewer and businessman and has good non sinister reasons for not doing a review of that product. Just let it go and look for a review of the new $8K model when the model comes out.

Troglo whatever is way off base. He has absolutely no clue as to why greg did not review it.

I know the reason having discussed it with Greg but I am not a liberty to disclose the reasons. Greg is a good person, a honest reviewer and businessman and has good non sinister reasons for not doing a review of that product. Just let it go and look for a review of the new $8K model when the model comes out.

I'm sorry if I offended, but I didn't realize Greg is allowed to say what he wants under the name Gregr. I also didn't realize WSR wasn't out to make money and loves to review fringe projectors which sell so little Sony has even given up on making newer models of that particular business unit entry point. I assumed he was like all other employees of a the corporate world where if he says something, does something, etc, he's representing his company and therefore has to do what he's told or risk getting fired. With this economy I didn't think he would want to risk such a thing.

The US is still capitalist, but not capitalist enough that people can do what they want off the clock. At the same time not socialist enough, people are forced to do things which don't generate income in order to be fair to everyone. We're in the middle, of those two extremes, with our masters being the corporations we work for.

So I'm glad Greg isn't bound to that world, working at WSR in Temecula California. Again, I apologize. I didn't mean to imply anything sinister. Nor did I wish to say his reviewing or business ethics were in question. But to just state this is the country I live in, and since he does too, has to obey the same business rules I do too.

I'm sorry if I offended, but I didn't realize Greg is allowed to say what he wants under the name Gregr.The only one, or thing, that has any say over what I post here is me (and the forum operators of course).

I also didn't realize WSR wasn't out to make money and loves to review fringe projectors which sell so little Sony has even given up on making newer models of that particular business unit entry point.WSR has no control over what I choose to review (although they could refuse to print a review, but only in its entirety - not edited for content). I decide what I review or don't review. If WSR wants something reviewed that I don't want to review, they simply send it to someone else to do a review. I've reviewed projectors priced at $70,000 in WSR - not exactly Best Buy type products.

I assumed he was like all other employees of a the corporate world where if he says something, does something, etc, he's representing his company and therefore has to do what he's told or risk getting fired. With this economy I didn't think he would want to risk such a thing.I'm not an employee of WSR, but they do pay me for my reviews. They would like me to do a review each month, and I would like to do none at all. But I still like to help support WSR because it's the only US magazine (I don't know the foreign magazines) that would print the type of detailed, semi-technical review that I write, so I continue to do reviews for them of products I want to review. WSR corrects the punctuation in my reviews (not always properly in my opinion) and excerpts the little teaser quotes you see sprinkled around in the layout. That's it. There are no attempts to influence what I write or what I say here (that would be just laughable).

So I'm glad Greg isn't bound to that world, working at WSR in Temecula California. Again, I apologize. I didn't mean to imply anything sinister. Nor did I wish to say his reviewing or business ethics were in question. But to just state this is the country I live in, and since he does too, has to obey the same business rules I do too.First, I don't work in Temecula. Second, I left that corporate business crap far behind, long ago. Third, I take consulting jobs only when something really interests me, and do reviews primarily to keep up with the technology and help out WSR. Most of the time I'd rather be on the golf course, watching movies, or playing my new electronic piano (CVP-409GP).

One day after Greg has given up on these forums, because he became tired of constantly having his credibility and motives questioned, we will all question why he stopped posting. There are a handful of people, like Greg, who raise the level of discussion around here. Can we stop trying to drag them down into the gutter with the rest of us?

Can we stop trying to drag them down into the gutter with the rest of us?

Nor should anyone seek to unnecessarily elevate them.

No one should be immune from having their work scrutinized, or motives questioned. Experts,whether self proclaimed, or otherwise, should be held to an even higher standard than the rest of us. Any suggestion to the contrary would simply be sycophantic censorship.

Maybe the thread should get back on topic

Nor should anyone seek to unnecessarily elevate them.

No one should be immune from having their work scrutinized, or motives questioned. Experts,whether self proclaimed, or otherwise, should be held to an even higher standard than the rest of us. Any suggestion to the contrary would simply be sycophantic censorship.

Maybe the thread should get back on topic


By all means scrutinize Greg's, or anyone else's, work. It should rise and fall on how good it is. If there was any scrutinization in troglobite's posts, I missed it. Instead, his posts contain what appear to be an attack on Greg's objectivity for being part of what he calls "socialist corporate capitalism."

Now, after I have had the last work on this, I agree that this thread should get back on topic. :)

Nor should anyone seek to unnecessarily elevate them.

No one should be immune from having their work scrutinized, or motives questioned. Experts,whether self proclaimed, or otherwise, should be held to an even higher standard than the rest of us. Any suggestion to the contrary would simply be sycophantic censorship.

Maybe the thread should get back on topic

I agree with everything except the bolded part. Baseless accusations are a waste of bandwidth. If Troglobite knows something specific about Greg's motivations, that's fine. But all I saw in Troglobite's post was general stereotyping (essentially 'I believe everyone in Greg's industry does this, so Greg must too'). That kind of stuff reveals more about Troglobite's motivation than Greg's.

Let's say someone spent a lot of time and effort making objective comparisons between projectors, and posted his conclusion that Sim2 is the best. I don't believe blind accusations that he's paid off by Sim2 are justified, do you ;)

Now, after I have had the last work on this, I agree that this thread should get back on topic. :)

Shouldn't that be "word", rather than "work".

Back at you baby:D:D

Shouldn't that be "word", rather than "work".

Back at you baby:D:D

I'll fire my secretary. :D

Let's say someone spent a lot of time and effort making objective comparisons between projectors, and posted his conclusion that Sim2 is the best. I don't believe blind accusations that he's paid off by Sim2 are justified, do you ;)

If that "someone" made such a universal, purely brand based, declaration, I would certainly be suspicious. If were were based on specific models, and reporting was ,as you say, objective, that's a whole different ball game.

Even then, I would still defend the right of people to question anyone's motives, my own included.

I`m off to the US open at Bethpage. Alas, only to watch practice on Tuesday. Sure going to miss this thread while I`m gone. NOT.

Even then, I would still defend the right of people to question anyone's motives, my own included.

There is no line between questioning one's motives and attacking one's character. They are the same thing. If a line can be drawn between then, I am incapable of drawing it.

I think that everyone has bias. It is part of being human. It is almost irrelevant. Biased people can be wrong. They can also be right. Why not just evaluate what is said, rather than who is saying it?

Plus, although I can't find it, I would assume that there has to be some kind of forum rule prohibiting this kind of conduct. If there isn't there should be.

There is no line between questioning one's motives and attacking one's character. They are the same thing. If a line can be drawn between then, I am incapable of drawing it.

I think that everyone has bias. It is part of being human. It is almost irrelevant. Biased people can be wrong. They can also be right. Why not just evaluate what is said, rather than who is saying it?

Plus, although I can't find it, I would assume that there has to be some kind of forum rule prohibiting this kind of conduct. If there isn't there should be.

Word.:D

The only one, or thing, that has any say over what I post here is me (and the forum operators of course).

Alright, fair enough.

Instead, his posts contain what appear to be an attack on Greg's objectivity

I already said I meant no such words. I even apologized if that was even implied. I was only trying to point out, he works for another, so therefore it's possible he isn't allowed to say anything about the VW200, etc. Based upon the fact he still refuses any comments, but that's his business why or why not he says nothing.

If Troglobite knows something specific about Greg's motivations, that's fine. But all I saw in Troglobite's post was general stereotyping (essentially 'I believe everyone in Greg's industry does this, so Greg must too'). That kind of stuff reveals more about Troglobite's motivation than Greg's.

Very true, it reveals I know from experience of what I speak. I too am in the freelance writer industry.

Back when chat rooms were popular a friend of mine, who was also a writer, said some smart ass comments about handicapped people. He was stupid enough to use his real name that was linked to his AOL account. This was about I'd say 13 years ago. Anyway, word got around it was him who said these things. Even though it was supposedly a "private" chat room, which was definitely more private than this forum. Since then he's not gotten another assignment and had to find another line of work.

This industry sucks and you can't ever speak your mind. Every word you say is monitored and you're a prisoner to your own words. You're their bitch. That's why I'm now in my third year of premed with one more to go before med school. I'm tired of it all.