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post #271 of 522 Old 01-16-2009, 12:33 AM
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Originally Posted by odyssey View Post

You scale the highest level up to full white, adjust all the other levels so that the proportion between levels stays the same and close the aperture so that the highest level comes back to the original illumination. The result is that the gamma stays the same, except that black is now lower. Greg calls this no dynamic gamma. The second effect is that stray light is blocked by the smaller aperture, further increasing sequential CR.

odyssey, how is the initial scaling up of brightness accomplished? If it's done by pushing up the IRE of pixels then it sounds suspiciously like dynamic gamma even though the output gamma may be unchanged. I suspect that there is more going on otherwise I don't think gregr would have specifically said it's not dynamic gamma. Perhaps it's an increase in lamp brightness coupled with the iris closing. I guess there isn't a point in speculating though until more information comes out.

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Originally Posted by Darinp2 View Post

I think of that as having a dynamic gamma since the signal to the chips has to be modified to counteract the iris closing, but I see what he is saying. The above approach basically has the ultimate brightness compression, i.e. clipping. But it can be controlled by not being too aggressive. They wouldn't want to jump between two very different iris positions if an image with say 60 IRE as the brightest all of a sudden had a couple 100 IRE pixels show and then disappear unless they were okay with visible image pumping, so clipping in some cases would be necessary.

Yes I think of it as dynamic gamma too but only if the mechanism used is pushing the IRE's of the pixels while the iris is closed. But that may not be the case (I didn't read the article).

One question though, how are you using the term clipping compared to BC? In a normal DI if just enough dynamic gamma is applied to exactly counteract the brightness loss of the iris (and there is no other headroom mechanism available to boost brightness) the brightness can't be boosted beyond about 50IRE or so and everything from 50-100IRE is completely crushed. Is this what you are referring to as clipping?

The diagram below better describes what I'm saying (w/ measurements off of a Pearl). The bottom curve is normal iris off (measured from Pearl). The curve above it represents non-aggressive dynamic gamma algorithm where the brightness is not pushed to exactly compensate for the loss of brightness of the DI and this in turn allows the brightness to increase in the 50-100IRE range albeit with some compression (also measured from Pearl). The green and white curve represents a theoretical aggressive dynamic gamma algorithm where the brightness is boosted to exactly compensate for the iris closing but by around 50IRE the pixels have been pushed to max brightness so there is no more brightness to be had and everything gets completely crushed from that point on. Is that the range that you are calling clipping?



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post #272 of 522 Old 01-16-2009, 01:10 AM
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Quote:
Originally Posted by Mark Petersen View Post

One question though, how are you using the term clipping compared to BC? In a normal DI if just enough dynamic gamma is applied to exactly counteract the brightness loss of the iris (and there is no other headroom mechanism available to boost brightness) the brightness can't be boosted beyond about 50IRE or so and everything from 50-100IRE is completely crushed. Is this what you are referring to as clipping?

Yes. But the amount that gets crushed/clipped depends on the iris position. If the iris only shuts down 2x for a specific scene then only things above about 75 IRE (specific point depends on gamma) would get clipped (assuming no headroom). For a 2.4 gamma and this kind of system a 3.5x multiplier would mean things above about 60 IRE would get crushed when the iris was at its most closed.

Sony basically keeps the multipliers for the gamma adjustment lower than the amount the iris shut down so that they get brightness compression (or high IRE compression) instead of crushing/clipping. I think they also leave themselves some headroom. I suspect that after Greg's initial analysis of an early DI implementation by them pointed out the brightness compression issue Sony decided to not be as aggressive with their dynamic gamma/compensation to the signal for the iris shutdown effect. I think it has been easier for people to see brightness compression issues with test patterns than to see the negative side of not enough adjustment of the signal and so going that way has made sense for Sony even though it likely has meant less improvement to many images than they could have achieved with more aggressive gamma adjustment.

It will be interesting to see what kind of multiplier the Lumis has for dynamic on/off CR to native or static on/off CR with everything open. My gut feeling is that it is probably less than 3.5x in calibrated modes if no bad side effects of the DI are visible, but I could be wrong.

--Darin

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post #273 of 522 Old 01-16-2009, 01:15 AM
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Originally Posted by coldmachine View Post

Here's a single pixel star field. No hazing or ghosting BS anywhere. Very deep blacks with piercing white stars.



CM,

First of all, thanks a lot for posting the magnificent screen shots! They are eye-popping to say the least! I've posted the one above only so as to not take up too much space. That one is incredible.
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post #274 of 522 Old 01-16-2009, 02:57 AM
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Originally Posted by thebland View Post

How much light would you lose zooming with the Lumis? Could anyone measure? If I pick this up I'll be at max zoom with the T2 lens. Any idrea how much light i'll lose?

Thanks!


you should expect arround 20-30% depends on the zoom position and than you are safe.

as the lumis offer 3 different optics i am sure you will not lose to much.
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post #275 of 522 Old 01-16-2009, 04:26 AM
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Thanks CM for the great pictures.

You would think that it would be easy to find a dealer in the NYC area who would be able to demo one (if not now then maybe in a few weeks) but it is not.

The single pixel star field image is an interesting pattern. Can you tell what exactly the iris is doing there? Assuming the single pixel stars are 100 IRE and the black field is 0, you would expect from Greg's explanation of at least Planar's DynamicBlack implementation, that the 100 IRE stars could not be increased further. Perhaps by disabling DynamicBlack while using this pattern you can tell if Mark and other are right about headroom in the lamp? It would also be interesting to see if the choice the Iris makes in those kinds of scenes is to maximize blacks or brightness.

Thanks for your posts.

Affable Nitwit
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post #276 of 522 Old 01-16-2009, 05:14 AM
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Quote:
Originally Posted by darinp2 View Post

In Planar's case the dynamic iris isn't in the lens, so I wonder how much it improves the static on/off CR. Also, SIM2's isn't in the lens and from what I've heard about it I'm not sure if the static on/off CR with the iris/mechanism closed down would be better than the static on/off CR with it open either.

--Darin

The sequential CR does increase with decreasing aperture size in the illumination system before the DMDs. The reason is the same as with lens apertures: stray light is blocked and has a much higher percentage effect on the off state versus white. The illumination system aperture is the current modification of the Barco DCI projectors. The CR increase is from about 2200:1 to 5000:1 and the former TI engineer who developed the aperture technique thinks that a matching smaller lens aperture will not increase the sequential CR significantly further. I am not sure about this and will be testing it soon. Also, these current mods use round apertures to help maintain acceptable uniformity. Uniformity is a very serious problem with decreasing aperture size.
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post #277 of 522 Old 01-16-2009, 06:31 AM
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Quote:
Originally Posted by GetGray View Post

You can go find the spreadsheet I posted on the C3X1080 for Bruzonsky. (His thread, this forum, somethign about C3X). I measured the light output through the zoom range It's in a graph in a tab of that xls. I expect it would be similar, relatively. It was pretty linear in Steve's unit.

HTH, Scott

Very nice!!!

I can see at 2.46 I'll lose ~ 20% at this zoom vs '0' zoom (with iris closed at hi power).

***Now, CM or Alan... when you measured the light output... where are you in terms of throw ratio?? I'm at 2.46... I'f you are in the middle or close to 2.46, then the light loss, for me, will be negligible.

Light output is the major determinant for me..

Thanks!!


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post #278 of 522 Old 01-16-2009, 06:40 AM
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This is looking at every turn as one of the best things to come along. An ANSI CR measurement would be nice. Also a pic of the edge of the screen (if there is a velvet border) with some of the patterns.

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post #279 of 522 Old 01-16-2009, 07:32 AM
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time for nice screenshots
Jason ?
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post #280 of 522 Old 01-16-2009, 08:15 AM
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Originally Posted by Digital2004 View Post

time for nice screenshots
Jason ?

Dont worry, its in hand.

A scene like this is absolutely incredible on the Lumis. This image would bring most PJs to a standstill.

The camera is nowhere near handling this image properly. There is no banding, hazing or anything.

The very high ANSI cr is very apparent on the actual screen. One of my favorites.

The central dark band suffers no washout whatsoever, despite proximity of the very bright nucleus and cloud. There is actual single pixel detail, still intact, in there.



Who doesnt love a Shuttle shot?



The color and detail of this shot only hint at the real images intensity and impact. The camera is losing some of the color detail , as the image is so intense. In real life, this is a big, heavy, solid slab of 3 chip power.



If you're not lovin yourself some Helix Nebula, your some special kinda douche.



NYC



So good they framed it twice Not an easy shot for most PJs




As you can see the previous shots, these are all done by hand on a cheap little Sony.

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post #281 of 522 Old 01-16-2009, 08:37 AM
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Quote:
Originally Posted by Digital2004 View Post

time for nice screenshots
Jason ?

Quote:
Originally Posted by coldmachine View Post

Dont worry, its in hand.

That sounds really bad.
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post #282 of 522 Old 01-16-2009, 08:51 AM - Thread Starter
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I just ordered a new Minolta T-10 light meter. Will have it tomorrow.
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post #283 of 522 Old 01-16-2009, 09:07 AM
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I normally don't pay much attention to screenshots, but those are spectacular!! The wait for my projector is killing me.

Phil
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post #284 of 522 Old 01-16-2009, 09:36 AM
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Some very difficult geometry handled well, with some HF detail to handle as well. The detail on screen from the trees an buildings is very impressive



CGI Bubbles with exceptional line definition, great color detail and shading is also there.


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post #285 of 522 Old 01-16-2009, 09:55 AM
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I normally don't pay much attention to screenshots, but those are spectacular!! The wait for my projector is killing me.

+1

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post #286 of 522 Old 01-16-2009, 10:14 AM
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Quote:
Originally Posted by darinp2 View Post

Yes. But the amount that gets crushed/clipped depends on the iris position. If the iris only shuts down 2x for a specific scene then only things above about 75 IRE (specific point depends on gamma) would get clipped (assuming no headroom). For a 2.4 gamma and this kind of system a 3.5x multiplier would mean things above about 60 IRE would get crushed when the iris was at its most closed.

Yes exactly. If the amount of dynamic gamma being applied correlates with iris aperture then a smaller iris results in less dynamic gamma and less BC. I just wasn't sure if I understood how the term clipping (compared to BC) was being used. I suspect that gregr in talking about the Planar may be using the term to mean something other than the complete crushing that we're talking about with a more conventional DI implementation like the Sony.

Quote:


Sony basically keeps the multipliers for the gamma adjustment lower than the amount the iris shut down so that they get brightness compression (or high IRE compression) instead of crushing/clipping. I think they also leave themselves some headroom. I suspect that after Greg's initial analysis of an early DI implementation by them pointed out the brightness compression issue Sony decided to not be as aggressive with their dynamic gamma/compensation to the signal for the iris shutdown effect. I think it has been easier for people to see brightness compression issues with test patterns than to see the negative side of not enough adjustment of the signal and so going that way has made sense for Sony even though it likely has meant less improvement to many images than they could have achieved with more aggressive gamma adjustment.

Yes the amount of dynamic gamma can be less than what is needed to counteract the loss of brightness from the iris and this will also reserve more headroom (less BC in the upper region). I also agree that it's harder to spot BC while the improved black level is more of a first order effect and very noticeable, which is why usage of a DI is such a good tradeoff in dark scenes.

Quote:


It will be interesting to see what kind of multiplier the Lumis has for dynamic on/off CR to native or static on/off CR with everything open. My gut feeling is that it is probably less than 3.5x in calibrated modes if no bad side effects of the DI are visible, but I could be wrong.

It sounds as though the Planar and also the Lumis are different animals altogether and probably don't apply dynamic gamma (at least thats the sense that I got from the paraphrased comments from gregr in this thread). I'd love to know more about how the Sim2 works, but if they have invested a lot of money into R&D and have come up with something proprietary they may be reluctant to talk openly about it. I guess I'll have to wait until I can get my hands on one (which may be a long wait )


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post #287 of 522 Old 01-16-2009, 10:19 AM
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Quote:
Originally Posted by odyssey View Post

The sequential CR does increase with decreasing aperture size in the illumination system before the DMDs. The reason is the same as with lens apertures: stray light is blocked and has a much higher percentage effect on the off state versus white. The illumination system aperture is the current modification of the Barco DCI projectors. The CR increase is from about 2200:1 to 5000:1 and the former TI engineer who developed the aperture technique thinks that a matching smaller lens aperture will not increase the sequential CR significantly further.

So almost a 2x improvement in contrast which is great but still short of the 3.5x number being tossed around in this thread. So it sounds like something else is going on.

Quote:
I am not sure about this and will be testing it soon. Also, these current mods use round apertures to help maintain acceptable uniformity. Uniformity is a very serious problem with decreasing aperture size.

Sounds interesting, do you mind posting the results of your tests? Mod'ing the illumination system in DLP systems seems to be yielding pretty dramatic results and adding some excitement into this technology. I'd like to hear more about it.

Since the iris is in the illumination system (before the panels) the uniformity problem stems from the lack of uniformity in the lamp itself correct?


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post #288 of 522 Old 01-16-2009, 10:23 AM
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Wow! Those screenshots are really impressive
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post #289 of 522 Old 01-16-2009, 10:32 AM
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Quote:
Originally Posted by Mark Petersen View Post

I also agree that it's harder to spot BC while the improved black level is more of a first order effect and very noticeable, which is why usage of a DI is such a good tradeoff in dark scenes.

I probably didn't word it very well, but what I meant is that the problem of BC is easier for people to see than not compensating enough as the iris is closed down. For instance, if the iris closes down 4x for a 20 IRE on 0 IRE image and the 20 IRE stuff is only increased by 2x people won't necessarily know that. I haven't seen as much of people measuring that as looking for BC, where the AVS test disc even has a specific pattern to show BC. So, this gives an incentive to Sony to avoid BC more even if it means that 20 IRE on 0 IRE image has less intra-image CR.
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So almost a 2x improvement in contrast which is great but still short of the 3.5x number being tossed around in this thread.

I thought the 3.5x number was for dynamic on/off CR where odyssey was talking about improvement to native/static on/off CR.

--Darin

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post #290 of 522 Old 01-16-2009, 10:47 AM
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Originally Posted by Alan Gouger View Post

Kevin you want one that is large enough to pass the entire image at an angle. Heres what I bought. Plenty big. I tape it to the projector.

http://www.bhphotovideo.com/c/produc...l_Density.html

Alan, do you have a picture of what it looks like taped to your projector?

Also, does anyone know any dealers in Vancouver, BC that will be selling this projector? I only know of one Sim2 dealer here and apparently they just closed down, and the Sim2 site doesn't list any.
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post #291 of 522 Old 01-16-2009, 10:48 AM
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2 Questions:

1. Could you use the Host ONLY as it is needed with its digital connection to the LUMIS to run the machine with no video Inputs or output and substitute a VP (e.g. Lumagen Radiance) for the DVI video input on the machine?? So, use a Host to run it with no vieo connection/input and a VP for all video handling??

2. Where does the hot air exhaust come from? Left, Right, Rear??

3. Does the PJ accept RS-232 or is all RS-232 done via the Host RS-232 input (so, no RS-232 cable needed for Lumis itself)??


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post #292 of 522 Old 01-16-2009, 10:53 AM
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If I remember right, Greg talks about a 3.5x factor for the Planar, resulting in about 9000:1. The native for these projectors with current DMDs and open apertures is about 2500:1. SIM2 is claiming 30,000:1 or 35,000:1. That would be at least 12x. I don't think that is possible without some problems. I will know better in about two weeks.
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post #293 of 522 Old 01-16-2009, 11:11 AM
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Quote:
Originally Posted by thebland View Post

2 Questions:

1. Could you use the Host ONLY as it is needed with its digital connection to the LUMIS to run the machine with no video Inputs or output and substitute a VP (e.g. Lumagen Radiance) for the DVI video input on the machine?? So, use a Host to run it with no vieo connection/input and a VP for all video handling??

2. Where does the hot air exhaust come from? Left, Right, Rear??

3. Does the PJ accept RS-232 or is all RS-232 done via the Host RS-232 input (so, no RS-232 cable needed for Lumis itself)??

1. If you mean can you simply plug in a VP to a single HOST i/p and use the VP to handle your sources.....Yes.

2. Its vented at the rear corners.

3. All via the HOST unit. Only the fiber needs to go to the PJ.

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post #294 of 522 Old 01-16-2009, 11:15 AM
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Quote:
Originally Posted by coldmachine View Post

1. If you mean can you simply plug in a VP to a single HOST i/p and use the VP to handle your sources.....Yes.

2. Its vented at the rear corners.

3. All via the HOST unit. Only the fiber needs to go to the PJ.


Sounds good. Thanks!~


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post #295 of 522 Old 01-16-2009, 11:20 AM
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How long is the stock fiber cable? I asked before somewhere, if someone replied and I missed it, sorry.


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post #296 of 522 Old 01-16-2009, 11:21 AM
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Quote:
Originally Posted by odyssey View Post

The sequential CR does increase with decreasing aperture size in the illumination system before the DMDs.

I definitely agree that it can when done right. From what I have heard about SIM2's system I'm not sure if it does or does much. It could, but I'm just not sure. It should depend on multiple factors, including what the openings are before they start closing the DI down.
Quote:
Originally Posted by odyssey View Post

The reason is the same as with lens apertures: stray light is blocked and has a much higher percentage effect on the off state versus white. The illumination system aperture is the current modification of the Barco DCI projectors. The CR increase is from about 2200:1 to 5000:1 and the former TI engineer who developed the aperture technique thinks that a matching smaller lens aperture will not increase the sequential CR significantly further.

With that much improvement it sounds to me like the opening in the lens and the opening before the DMDs were not matched up well before this iris was added. I wonder how much those DCI DMDs are capable of under ideal conditions and ignoring uniformity. I'm not sure what they have for those as far as black backing, dimple issues, etc. compared to consumer chips. I was able to get about 9k:1 on/off CR with an Optoma H79 over 3 years ago with a fixed dual iris system. It came at the expense of uniformity and light output, but I felt it was worth it with my High Power screen in my dark theater.

I think of some of this iris stuff (with DLPs at least) as going beyond what I think of as more of a traditional view of just blocking off axis light, or what might be thought of as bad light. I'll cover what I mean and you can add or correct things if you want.

Think of a cross section of the lens where an iris will go as a quarter shape and size. Then an iris in this same plane as dime shape and size. Then put an opening before the DMDs that perfectly lines up with that dime shape in the lens. If we look at the light going through that dime shape in the lens for white and black the amount of light is basically the area times the amount of light per area. Let's assume for a second that the white going through that dime shape is coming straight off the mirrors to that opening and is uniform at that point, while the black is bouncing around inside that chamber and is uniform as it hits the quarter sized shape in the lens. This basically means that the native CR of the chips is high to a spot, but they bounce some light fairly randomly (like off the dimple, mirror corners, etc.) Of course this is all looking at a pretty idealized case to get the point across and how much of this is relevant to real cases depends on how much the chips can actually do. Anyway, even though in this case the white is going through the dime shape uniformly and so could be though of as on-axis light, I think there is an opportunity to improve the on/off CR further by blocking some of it.

Considering the above case, block half the dime shape in the lens. What happens here is that the white level goes down to half and so does the black level, since both are uniform across that area and the area is half. So, no improvement to on/off CR. But now go into the opening before the DMDs and block half of it in a way that perfectly lines up with the new half-dime shape in the lens. In theory the white level wouldn't drop here because the 2 openings are lined up perfectly (in reality it likely drops a little). But the key here as that the amount of light that hits the DMD has gone to half and the black level across the quarter shape in the lens has dropped to half. So, white went to half by closing both irises down, but the black level went to 1/4th, meaning on/off CR doubled.

The further the on/off CR of the projector is from what the chips are capable of the more I think the above applies. As things approach the CR that the chips can do for light traveling basically straight to the dime opening in the lens (not bouncing off walls before getting there), the less the above applies. At least that is how it looks from my experience and understanding.

When I was doing something like you are considering with putting a smaller lens iris in, the way I approached it was to take all the front elements out of the H79 lens until I got back to the one with the iris. I put a piece of white paper on something so that I could put it back in the lens and see what the light looked like at that opening for black and for a full field of gray or white. If you did something like this (might want to use sunglasses or stronger ) then I think you could get a reasonable idea about whether a smaller opening in the lens would improve your on/off CR. If for something like a 20 IRE gray field you saw that most of the light coming through the lens was concentrated in one area and a video black image didn't have the same pattern then you could probably improve your on/off CR by changing the opening to block the parts that are dimmer for that full field gray. And by looking at the video black image you might be able to see more issue with black coming through one spot in the opening than another.

If you try this I'll be interested to hear what your findings are.

--Darin

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post #297 of 522 Old 01-16-2009, 11:37 AM
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Originally Posted by odyssey View Post

If I remember right, Greg talks about a 3.5x factor for the Planar, resulting in about 9000:1. The native for these projectors with current DMDs and open apertures is about 2500:1. SIM2 is claiming 30,000:1 or 35,000:1. That would be at least 12x. I don't think that is possible without some problems. I will know better in about two weeks.

I'm pretty sure coldmachine said that he was getting around 9k:1 native with his C3x1080. I don't know if they have opened the apertures further for full white with the Lumis than the C3x1080, but if not then I think they are in a reasonable range if they start with 9k:1 and end up with 20k:1 or low 20s. I know their spec is higher, but most of these end up at least a little lower than their specs after calibration.

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post #298 of 522 Old 01-16-2009, 11:50 AM
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Originally Posted by darinp2 View Post

I'm pretty sure coldmachine said that he was getting around 9k:1 native with his C3x1080. I don't know if they have opened the apertures further for full white with the Lumis than the C3x1080, but if not then I think they are in a reasonable range if they start with 9k:1 and end up with 20k:1 or low 20s. I know their spec is higher, but most of these end up at least a little lower than their specs after calibration.

--Darin

If it is 9000:1, it is with aperture(s) smaller than usual.
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post #299 of 522 Old 01-16-2009, 12:05 PM - Thread Starter
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I think the lamp modulation is a big part of what we are seeing here aside from just the iris.
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post #300 of 522 Old 01-16-2009, 12:11 PM
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Originally Posted by Alan Gouger View Post

I think the lamp modulation is a big part of what we are seeing here aside from just the iris.

I think you're right.

I don't believe this unit is about DB or the iris placement or the modulation or the analysis or the synchronization.

Its about all of them running together and the control system that achieves that.

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