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AVS Contrast Thread - Now with Dynamic Contrast Results! - Page 2

post #31 of 200
Thread Starter 
Quote:
Originally Posted by stanger89 View Post

Credits would be a good one. Star Fields, perhaps the scene where they approach the Death Star in Star Wars (Falcon/Death Star take up a small portion of the screen but are brightly lit on a black back drop).

Yup, those would all be good test cases. I don't think that most people would notice the reduced intra-scene contrast of a DI equipped projector like a Pearl or Black Pearl. On a side by side comparison with dark scenes though the difference should be relatively easy to spot (brighter whites on the higher native contrast machine). BC will be even more difficult to spot and it's dependent on the degree of gamma boost the DI projector uses.
post #32 of 200
Isn't it true that the smaller the iris gets, the higher the on/off contrast ratio will be for that given setting?

For dlp projectors, having the iris wide open amounts to a 2000:1 contrast ratio. Setting it on a high contrast setting can get you upwards of 5-8000:1 or so. Of course at the high contrast setting, the iris still needs to let out a decent amount of light, as the 100 ire still needs to be considered bright.

Would the same apply to LCOS or LCD? So the native contrast of the pearl may be around 3000:1 (sorry not too sure about that number), but with the closing of the iris, wouldn't that mean that the on/off would jump up as well, to the point where it is almost completely closed, and the resulting contrast would be very high?

For instance, if the iris of the pearl was set at it's smallest point and kept at that setting, what then would the on/off contrast ratio be. Shouldn't it be significantly larger than it's native amount, if this is consistent with what occures in dlp's?
post #33 of 200
Quote:
Originally Posted by johnsmith808 View Post

Isn't it true that the smaller the iris gets, the higher the on/off contrast ratio will be for that given setting?

Only when you are talking about the ratio between on=no iris and off=Iris-on. The native CR really never changes, just the light output. This is why the "bright whites" get quite dim in Iris-on mode during dark scenes.
post #34 of 200
Quote:
Originally Posted by johnsmith808 View Post

Isn't it true that the smaller the iris gets, the higher the on/off contrast ratio will be for that given setting?

That is correct, as the apreture of the iris is decreased the CR increases, but lumens descrease. The CR increases because in the off state, a higher percentage of stray light is blocked by the iris than in the on state. IIMU that this CR increase is only substantial for the reflective designs (DLP and LCOS/SXRD) Lens iris CR impact on transmissive LCDs are minimal.
Quote:
Originally Posted by johnsmith808 View Post

For instance, if the iris of the pearl was set at it's smallest point and kept at that setting, what then would the on/off contrast ratio be. Shouldn't it be significantly larger than it's native amount, if this is consistent with what occures in dlp's?

The Ruby and the Pearl both use the same 0.61" SXRD panel rated at 5,000:1 CR. Iris max apreture the Ruby measured d65 3,000:1. Iris min apreture measured d65 5,200:1, >70% increase in native CR.
post #35 of 200
Quote:
Originally Posted by GlenC View Post

The native CR really never changes, just the light output.

That is incorrect!
post #36 of 200
Thread Starter 
Quote:
Originally Posted by johnsmith808 View Post

Isn't it true that the smaller the iris gets, the higher the on/off contrast ratio will be for that given setting?

As HHF mentioned it is true that adding an iris will increase on/off contrast. It affects each technology (DLP, LCOS) a little differently and the results are a little different depending on where in the light path it's installed and the shape of the iris but there is no doubt that it improves intraimage contrast (also sometimes called static or simultaneous contrast) to varying degrees. For obvious reasons an iris primarily reduces the light around the edges of a projected beam and statistically this portion of the beam contains more scattered light so that even though the iris reduces the overall amount of light, the black level is reduced a little bit more and the contrast ratio is increased.

For the Pearl I measured 3200:1 without iris and ~4000:1 in Auto1 with smallest aperture for a relatively modest improvement of 25% simultaneous contrast. I haven't measured a Ruby but it's possible that the manual iris modes close down even more than the Pearl Auto Iris modes which would probably explain some of the differences in numbers between what I measured and what HHF quoted.
post #37 of 200
So dlp's seem to benefit the most with an iris, yet ironically enough, they don't seem to be able to effectively utilize a DI. I wonder what the on/off contrast of a dlp would be if the aperture size was as small as the Ruby's smallest setting? Makes you wonder how awesome dlp could be if it could work with an iris as well as the Sony's.
post #38 of 200
Quote:
Originally Posted by Mark Petersen View Post

........For the Pearl I measured 3200:1 without iris and ~4000:1 in Auto1 with smallest aperture for a relatively modest improvement of 25% simultaneous contrast.......

This is what I consider to be the "native CR really never changes", just eliminating some light path issues. It doesn't create the significant change from 3200:1 to 10,000:1, or what ever is reported as CR on/off performance on projectors with irises.
post #39 of 200
Quote:
Originally Posted by GlenC View Post

This is what I consider to be the "native CR really never changes", just eliminating some light path issues. It doesn't create the significant change from 3200:1 to 10,000:1, or what ever is reported as CR on/off performance on projectors with irises.

The Sharp 12K goes from 1,000:1 iris off to 3,500:1 with both lamp and lens iris on!
post #40 of 200
Quote:
Originally Posted by HoustonHoyaFan View Post

The Sharp 12K goes from 1,000:1 iris off to 3,500:1 with both lamp and lens iris on!

IMO, 1000:1 CR is totally useless, 3500:1 is very poor....... I need to see 20000:1 or better for really good performance. I would like to see better blacks on my RS1 and need to consider a ND filter, I cannot go bigger than 110" (16x9) to further reduce black level.
post #41 of 200
Thread Starter 
Quote:
Originally Posted by johnsmith808 View Post

So dlp's seem to benefit the most with an iris, yet ironically enough, they don't seem to be able to effectively utilize a DI. I wonder what the on/off contrast of a dlp would be if the aperture size was as small as the Ruby's smallest setting? Makes you wonder how awesome dlp could be if it could work with an iris as well as the Sony's.

Very true. So far it's a bit of a mystery why a DI hasn't made it's way to DLP.

Quote:
Originally Posted by GlenC View Post

This is what I consider to be the "native CR really never changes", just eliminating some light path issues. It doesn't create the significant change from 3200:1 to 10,000:1, or what ever is reported as CR on/off performance on projectors with irises.

The term "native CR" is always a little confusing. Some people use it to mean panel only contrast and others the end system contrast which presumably would include the effects of an internal iris. I agree though that when it comes to DI equipped projectors the on/off contrast means something else than it traditionally has and what it does with a native projector. What most people are really interested in is maximum intra-image contrast (the 4000:1 number for the Ruby for example). Maximum intra-image contrast is defined and measured in this thread but there is currently no analog to it in industry.
post #42 of 200
Having read the information above, it would be good if I could run my AE1000 in manual iris mode, but there isn't an option in either the user menu or the service menu. I was thinking about opening mine up and trying to fix the iris in the 'minimum' position, to maximise the contrast. I currently use an ND4 filter, so if neccesary I could change it for my ND2 filter or no filter at all if this made the picture too dim.

What I wonder though is: Would disconnecting the circuit that drives the iris cause a problem with the projector? Would the iris move to fully closed or fully open, or just stay where it was when it was powered down (given that I wouldn't open it up with the power on obviously)? I would turn of the iris function in the menu so the PJ isn't trying to control something that is disconnected.

What do you guys think about this idea? Am I mad for even suggesting opening up my PJ or would it be very likely that it would work?
post #43 of 200
Thread Starter 
Quote:
Originally Posted by Kelvin1965S View Post

Having read the information above, it would be good if I could run my AE1000 in manual iris mode, but there isn't an option in either the user menu or the service menu. I was thinking about opening mine up and trying to fix the iris in the 'minimum' position, to maximise the contrast. I currently use an ND4 filter, so if neccesary I could change it for my ND2 filter or no filter at all if this made the picture too dim.

What I wonder though is: Would disconnecting the circuit that drives the iris cause a problem with the projector? Would the iris move to fully closed or fully open, or just stay where it was when it was powered down (given that I wouldn't open it up with the power on obviously)? I would turn of the iris function in the menu so the PJ isn't trying to control something that is disconnected.

What do you guys think about this idea? Am I mad for even suggesting opening up my PJ or would it be very likely that it would work?

I wish that all manufacturers would include a manual iris so that a person could dial in the amount of brightness that they want while also improving contrast. As you point out, using an ND filter to control brightness is less than ideal because instead of improving contrast it actually reduces it (intra-image contrast anyway).

A manual iris alone doesn't improve shadow contrast as does a DI but it also doesn't introduce BC and iris pump. I think some people would prefer a manual iris only setting over using DI's or ND's depending on their tastes and setup (particularly screen gain).

As far as what will happen if you disconnect the iris on the AE1000 goes, I have no idea if it will stay closed or if it's spring loaded and will relax open again. You can always experiment and then report back. I'm sure some of the AE1000 owners will be interested in your findings.
post #44 of 200
Quote:
Originally Posted by Kelvin1965S View Post

Having read the information above, it would be good if I could run my AE1000 in manual iris mode, but there isn't an option in either the user menu or the service menu. I was thinking about opening mine up and trying to fix the iris in the 'minimum' position, to maximise the contrast.

Keep in mind that the Panny iris AFAIK is a lamp iris. It does not have the same light scatter reduction as the lens iris used in the SXRD pjs! IIRC Panny does not use an "iris" per say. In the LCDs the had a "dual barn door" system which functioned as a lamp light regulator. In their 720P 3DLP DI, they used a "flag system.
post #45 of 200
Thread Starter 
Quote:
Originally Posted by HoustonHoyaFan View Post

Keep in mind that the Panny iris AFAIK is a lamp iris. It does not have the same light scatter reduction as the lens iris used in the SXRD pjs! IIRC Panny does not use an "iris" per say. In the LCDs the had a "dual barn door" system which functioned as a lamp light regulator. In their 720P 3DLP DI, they used a "flag system.

It would be interesting to see how the Panny performs on the same AVS intra-image contrast benchmarks used here. I might be able to finagle one from a friend...hmmmm
post #46 of 200
Quote:
Originally Posted by HoustonHoyaFan View Post

Keep in mind that the Panny iris AFAIK is a lamp iris.

I opened it up last night and can confirm that the iris is next to the lamp, just behind some kind of 'mottled' glass (?) diffuser panel. I could see which connector linked the iris to the mainboard, but deceided to leave it connected for now. The mechanism could easily be moved using a small 'Q-tip' and seemed like it could be wedged in any position as it isn't sprung. Gravity seems to cause it to stay into it's initial postion. I've no idea whether this intial position is fully bright or dim.

I'd only gain the slight ansi contrast drop caused by my ND2 filter, by fixing the iris manually and removing the filter. I don't think it is worth the risk or hassle.

Unfortuanately the longer I own this PJ, the more critical I'm getting about the poor black / intrascene contrast. I'm now seriously considering changing the PJ, but I need one that will work with a 20' throw from a shelf rather than coffee table or ceiling mount...but that's another thread I guess.
post #47 of 200
Dlp's really benefit from an iris when it comes to native contrast ratio. The one thing I wonder, though, is at what point does the benefit of having a narrower and narrower iris setting deminish?

For example, the Sharp MKII has around 1,300 with iris wide open, 3,000 or so with it on medium, and 4,300:1 with it in narrow. What if the iris could shut down even further? Would it be able to achieve a 6,000:1 contrast ratio?

Of course the loss of light would be significant at this point, but if one has a high gain screen, at least it could be an option.
post #48 of 200
Quote:
Originally Posted by johnsmith808 View Post

Dlp's really benefit from an iris when it comes to native contrast ratio. The one thing I wonder, though, is at what point does the benefit of having a narrower and narrower iris setting deminish?

For example, the Sharp MKII has around 1,300 with iris wide open, 3,000 or so with it on medium, and 4,300:1 with it in narrow. What if the iris could shut down even further? Would it be able to achieve a 6,000:1 contrast ratio?

Of course the loss of light would be significant at this point, but if one has a high gain screen, at least it could be an option.

Hi gain screen would put you back to square one. Why to buy a hi contrast pj with deep black level then boost that with a hi gain screen? Unless there are some screen material that have higher gamma characteristics.
I think the min aperture size is determined basically based on top lumen.
post #49 of 200
Quote:
Originally Posted by johnsmith808 View Post

Dlp's really benefit from an iris when it comes to native contrast ratio. The one thing I wonder, though, is at what point does the benefit of having a narrower and narrower iris setting deminish?

For example, the Sharp MKII has around 1,300 with iris wide open, 3,000 or so with it on medium, and 4,300:1 with it in narrow. What if the iris could shut down even further? Would it be able to achieve a 6,000:1 contrast ratio?

Of course the loss of light would be significant at this point, but if one has a high gain screen, at least it could be an option.

Even 6000:1 is poor, IMO, you need 3-4 times that.
post #50 of 200
Quote:
Originally Posted by CaspianM View Post

Hi gain screen would put you back to square one. Why to buy a hi contrast pj with deep black level then boost that with a hi gain screen? Unless there are some screen material that have higher gamma characteristics.
I think the min aperture size is determined basically based on top lumen.

While it's true that absolute black will be raised with a high gain screen, if it could allow you to run a higher on/off contrast ratio and still be sufficiently bright, might be worth it for some.

Example: Take the Sharp xv-z12k. With the narrow iris, you'll get around 4,500:1 with around 200+ lumens. Now what if that iris could be shut down even further, resulting in a 7,000:1 on/off contrast ratio, but the lumens would only be 100. Now throw in a screen with 2 or 3 gain, and you will have around 200-300 lumens, but with a much higher contrast ratio. Black level could end up being the same, but peak white will be higher.

I'm sure there is a limit as to how small the aperture can be set before the benefit diminishes, but I'm wondering if these dlp's with these irises have already reached that limit.

With the option of a high gain screen, the minimum aperture size will not be limited by a minimum lumen amount (which seems to be around 200 or so). The key word is option, as some will use that setting and some won't.
post #51 of 200
I don't use hi contrast screen for its associated problems such as hot spotting, narrow viewing angle and uniformity issue. For me that route is moot.

Going to such small iris size has its own problems with most obvious one "diffraction" which can be annoying and cause valuable ansi. So there is a point with no return in that approach with lens iris system..
post #52 of 200
Quote:
Originally Posted by johnsmith808 View Post

...I'm sure there is a limit as to how small the aperture can be set before the benefit diminishes, but I'm wondering if these dlp's with these irises have already reached that limit...

IIRC darinP (AVS CR guru) modified an Optoma H79 and got 8 or 9,000:1 on/off with << 200 lumens. He had it paired with a very high gain, >10 screen. Do a search in the archives for more info!
post #53 of 200
Quote:
Originally Posted by HoustonHoyaFan View Post

IIRC darinP (AVS CR guru) modified an Optoma H79 and got 8 or 9,000:1 on/off with << 200 lumens. He had it paired with a very high gain, >10 screen. Do a search in the archives for more info!

Wow! That's exactly what I was wondering about, but as always, when you wonder about something, someone already did it long before.

Makes you wonder how far dlp can go with usage of irises.
post #54 of 200
Quote:
Originally Posted by HoustonHoyaFan View Post

IIRC darinP (AVS CR guru) modified an Optoma H79 and got 8 or 9,000:1 on/off with << 200 lumens. He had it paired with a very high gain, >10 screen. Do a search in the archives for more info!

High gain screens would not be my direction. I would prefer to stay with a matte white smooth screen, now that we are in the 1920x1080 realm. Gain coatings compete with image resolution.

A 10+ gain screen is like trying to put a turbo and nitrous on a '85 Yugo....
post #55 of 200
Quote:
Originally Posted by GlenC View Post

High gain screens would not be my direction. I would prefer to stay with a matte white smooth screen, now that we are in the 1920x1080 realm. Gain coatings compete with image resolution.

A 10+ gain screen is like trying to put a turbo and nitrous on a '85 Yugo....

Like I said, it would be an option for some, and not for others. Needing a screen gain of 10+ is extreme, though. Maybe more around 3, with the high power. So you could get lumens down to 100, and get awesome contrast.

Shouldn't be too hard for manufactures to offer more iris settings, would it? I think the Benq 1000 has tons of them. Having only 3 iris settings seems too restrictive.
post #56 of 200
Quote:
Originally Posted by johnsmith808 View Post

Like I said, it would be an option for some, and not for others. Needing a screen gain of 10+ is extreme, though. Maybe more around 3, with the high power. So you could get lumens down to 100, and get awesome contrast.

Shouldn't be too hard for manufactures to offer more iris settings, would it? I think the Benq 1000 has tons of them. Having only 3 iris settings seems too restrictive.

The goal is to get the native CR of the projector above 30K:1, without any iris. Bright white next to deep black, like a star field.... real dynamic range in one scene.
post #57 of 200
Dynamic range is dynamic range whether the pj produces 200 lumens (a dlp with a variable manual iris) or 500 lumens (a dlp with the same contrast ratio, but acheives it without an iris).

Sounds like you are concerned with brightness, due to not liking screens with gain. So you will need 30k:1 contrast ratio and a certain brightness level. I would be happy with 30k:1 with lower lumens.
post #58 of 200
Quote:
Originally Posted by CaspianM View Post

Hi gain screen would put you back to square one. Why to buy a hi contrast pj with deep black level then boost that with a hi gain screen?

The main reason is in cases where that high contrast ratio isn't usable without a high gain screen (because ft-lamberts for white would be too low), so you would have to settle for lower CR (or maybe a different technology) if you aren't willing to use a high gain screen. Or so you can have a big screen at that same CR and still enough ft-lamberts for white. In the case mentioned, a person might have to settle for 1300:1 on/off CR if they were only willing to use a 1.0 gain screen, but could get 4300:1 if they were willing to go with a high gain screen that gave them say 2.5 gain at the main viewing position. They could also use that for movies and then open the iris up for some other things where they wanted higher ft-lamberts. For instance, if they preferred 12 ft-lamberts for movies, but 30+ for certain video games where they were willing to live with lower on/off CR. Or just wanted to open the irises up for things like the SuperBowl with lights on. If they were already at max lumens there wouldn't be an option to open up the irises for much brighter images for those other things compared to how they watch movies in the dark.
Quote:
Originally Posted by GlenC View Post

High gain screens would not be my direction. I would prefer to stay with a matte white smooth screen, now that we are in the 1920x1080 realm. Gain coatings compete with image resolution.

The High Power has very high image resolution.

As far as that 10+ gain screen, I tried it (the Mocom), but it has one of those silver surfaces and I don't like the speckling I see from any screens like that (the SilverStar for instance). I also dislike the SuperNova for the same kind of thing.

The H79 worked pretty well with the High Power and I preferred that. I went about as far down on the irises as I could go, but also had 4 irises total. Starting from the bulb, one red and one clear at one location prior to the DMD and then another red and clear at a location in the lens (after the DMD). I also optimized them for the particular zoom and offset I was using. They would need to be a little more general with if the zoom and offset weren't known.

My preference at this point (and even then) was for somebody to do a dynamic iris system that is as good as what Sony has on their projectors, but with a DLP. That is one way to get high lumens and high on/off CR. But 2 dynamic irises working in unison might work best with a DLP and not sure any company will go to that expense anytime soon. They do it for their irises that can be adjusted (by not dynamic) with one prior to the DMD and one after, but I'm guessing the upcoming BenQ with a dynamic iris will just have one of them moving. And I hope it works as well as Sony's implementation, but not banking on it yet.

--Darin
post #59 of 200
It would seem to me that a dynamic iris with a dlp would potentially be even better than with lcd or lcos, because even when it is shut way down, you won't suffer from brightness compression because the contrast ratio jumps so high! Imagine something like what you did with the H79, but dynamic! 9000:1 on/off, 600:1 ansi, no brightness compression. Not sure if anyone would be interested in that pj.
post #60 of 200
I don't understand.. How a hi gain such as HP can increase the on/off cr?
Hi gain is only a multiplier on both ends.
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