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Discussion Starter · #1 ·
I started considering this question: Will a brighter projector necessarily have better shadow detail even if the contrast ratio is the same?


If Projector A displays from 4 lumens to 2000 lumens and Projector B displays from 2 lumens to 1000 lumens they have identical contrast ratios, right?


However, the individual patches of "shadow" are brighter on the brighter pj. Is it easier for the eye to pick up differences in brighter material than dimmer material? Does that mean they it will be easier to differentiate the various dark patches on a brighter projector?


Does that mean really dark shadows are not conducive to shadow detail? I know that my 32" Proscan direct view has much poorer shadow detail that my 21N/38t. The shadows in the direct view tend to look like large patches of black with no detail.


Would the more saturated colors of an LCD give the eyes even more cues to distinguish the dark patches than less saturated (DLP) technologies?


Does increasing perceived brightness require adding lumens to a display in an arithmetic fashion or an exponential/geometric fashion? i.e. does it take increasingly larger amounts of lumens to notice the next perceivable increase in brightness? (Like increasing volume 3 decibels requires a doubling of power).


I had been thinking that 2000 minus 4 was 1996. With a 2000 lumen projector I would spread the available contrast (lightest to darkest scenes) over 1996 potential lumens. Whereas, on a 1000 lumen projector, I would have only 998 lumens to spread across the spectrum of scenes. It's like opening an accordion, all the folds(levels of brightness) get farther apart from each other. If this were true, then the brighter projector would always have more contrast.


Or is it that the eyes react to brighter scenes? Though that should make the darker patches look darker, I don't see how that would improve the perception of shadow detail.


Can anyone tell me how this all really works?


I'm kind of in the dark. (Heh.)
 

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The important aspect in assessing how you will experience contrast level, is absolute black and, naturally contrast rate / brightness.


A 5000 Ansi Lumen LCD with a contrast rate of 1000:1 would easilly be beaten by a Sony G90 CRT on perceived (and real) realism although the G90 is rated at 300 Ansi Lumen and about 1000:1.


Look for the BEST possible ABSOLUTE black level, in combination with maximum contrast (and brightness). The new HD2 DLP chips have the best blacks so far, besides CRT. I would not take a LCD even if it was thrown after me, at its current grey absolute blackness....


You can, however, compensate on low absolute black level by using lights. I currently own a plasma TV (and have owned several CRT, from Electrohome ECP 4500 to Barco 808s), and use lights to increase perceived blacks. This works extremely good, but is more difficult to implicate on a projector setup. My lighting is behind the TV set...
 

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Joe,


You're quite the thinker.


I think all of your ponderings are correct except this one:


"If this were true, then the brighter projector would always have more contrast."


CR is a ratio, not a difference, so the larger absolute lumen range of the brighter pj doesn't mean it has a higher CR.


I'm not sure what the answer is about perceoved brightness, although I know it is logarithmic.


You could try it yourself by putting an ND filter in front of your pj to cut light output. But you would have to eliminate ambient light for it to be a fair comparison.
 

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Jon Lygren,


Because the G90 can go completely black it would have a near infinite on/off contrast ratio.


Joe,


It is a very good question.


Let us first assume we are talking about projecting on to the same screen thus we have twice as much intensity when we go from the 1000 lumen to the 2000 lumen projector.


The eye typically tries to define the brightest thing it sees over a given period of time as white. As long as the intensity of either the 1000 lumen image and 2000 lumen image are enough to cause the pupil to dilate to the approriate size I think both images would be about the same visually once a periodic dark scene came up in the movie. I think if your intensity in ft-L was in the 20ft-L+ range either projector will give a similar image


However, If the projected image is very large and thus the intensity is low or the dark scenes are long then I think the brighter projector would have more dicernable shadow detail.


Notice I didn't say better. I think some people don't always want to be able to see every little detail in the shadows of a dark movie.


-Mr. Wigggles
 

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Discussion Starter · #5 ·
Noah,

I have tried the neutral density filter thing, thanks for reminding me. As I recall, from about two years ago now, everything did get darker, making colors appear to be slightly more saturated, but that may just have been an illusion due to their being dimmer, because when I took off the filter the colors seemed brighter again, which I preferred. Of course, the blacks were blacker, but the whites weren't as bright. I think it did nothing to improve shadow detail, and may have made it worse. But I didn't object because the dark patches looked like you weren't supposed to see anything there. I do remember that the differences I am talking about here were pretty subtle, even though I was cutting out 30% of the light. As I recall, the difference was so small I removed it based on being pretty sure I was wasting lumens, had to keep my room even darker, and lost some punch. Since the difference wasn't huge, this goes with what Wiggles is describing.


Wiggles,

Aside from listening to everyone here state axioms and trying to make sense of them, I have been trying to figure out what factors are primarily responsible for the better blacks and increased shadow detail of my 21N/38t LCD over an LP350 DLP. I suspect the absolute blacks may not be that superior on the LCD, and they might actually be the same or worse, as it is really hard to remember what a full black screen looked like on the 350. So just assuming the blacks are about the same, it has to be something else. Aside from apparent contrast, the big differences between the projectors are brightness and color intensity. So I have been trying to figure out how brightness helps apparent contrast.


It's good hearing from you again.
 

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What may be missing in this discussion is the gamma curve. One can imagine two projectors with exactly the same contrast ratios and black levels, but with two different gamma curves. The gamma of the projector, will make a big difference in the shadow details. A lower gamma value, e.g. 1.8 will make a sort of washed out looking image, but with great shadow details. A higher gamma, e.g. 2.6 will give a very "punchy" looking image, but with some loss of shadow detail.


Perhaps some of the differences you are seeing come from different gamma curves as well as contrast ratios and absolute black levels.


Steve
 

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Joe,


The XP21n definitely has a better contrast ratio then the LP350.


The LP350 might have had a little better black level but the XP21n is MUCH brighter probably 5 times brighter (seriously). This would mean that the XP21n has at least a 2:1 advantage in contrast ratio.


Getting back to original question about the two 1000:1 projectors... I would think of it exactly the same way as you would think of a volume knob on your stereo. Over a good sized range, the sound from different volume settings will sound very similar; but you don't want to have it too low or too high. Too high - you will not only hurt your ears but will expose every little low level hiss and hum in the recording. Too low - and you won't be able to hear all of the little details.


-Mr. Wigggles
 

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Discussion Starter · #8 ·
As to gamma, I can tell you that the 21N is both punchier and has much better shadow detial. As a matter of fact, my only real complaint about the 350 was the frustrating lack of shadow detail. At the time, I just thought that was the nature of projectors. The 21N cured me of that notion. It gave me what seemed like three times as much of everything, detail, brightness, color, contrast and shadow detail. That is still how it feels. If the gamma curve would make the 21N punchier at the expense of shadow detail, it doesn't need it. If a different curve would make it have better shadow detail at the expense of punch, it doesn't need that either.
 

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I can't say I'm an expert on this stuff, but I have thought about it and observed different kinds of projectors. Here's my take:

Quote:
Will a brighter projector necessarily have better shadow detail even if the contrast ratio is the same?
No, it will probably have worse shadows (because they absolute black will be brighter). But shadow detail should be about the same.

Quote:
If Projector A displays from 4 lumens to 2000 lumens and Projector B displays from 2 lumens to 1000 lumens they have identical contrast ratios, right?
Correct. Now lets look at a detail at 1IRE (1% of max brightness). That detail would put out 24 lumens on the brighter projector, and 12 lumens on the dimmer projector. Either level is enough above the 2-4 lumen black level to be clearly visible, since it's going to be 6 times as many lumens as black level, and we know black is clearly visible (we're not talking CRTs here). So you don't really have to worry much about losing range down there.

Quote:
However, the individual patches of "shadow" are brighter on the brighter pj. Is it easier for the eye to pick up differences in brighter material than dimmer material?
No, it's in general its actually harder to pick up differences in brighter material, since the ratio of image:black is going to be less. But in the example you gave that ratio will stay the same so it's nothing to even consider.

Quote:
Does that mean they it will be easier to differentiate the various dark patches on a brighter projector?
No. If that were beneficial, then people would turn up the brightness on their CRTs to give grey blacks. The reasons this would be bad should be obvious. The exception however is when the room isn't completely dark and the blacks will be washed out by light other than that of the projector. In that case it is helpful to increase brightness (black level) to overpower the ambient light. But lets leave that case aside for this discussion.

Quote:
Does that mean really dark shadows are not conducive to shadow detail? I know that my 32" Proscan direct view has much poorer shadow detail that my 21N/38t. The shadows in the direct view tend to look like large patches of black with no detail.
Sounds like you have the proscan adjusted incorrectly.

Quote:
Does increasing perceived brightness require adding lumens to a display in an arithmetic fashion or an exponential/geometric fashion? (Like increasing volume 3 decibels requires a doubling of power).
Exponential/geometric/logarithmic, just like audio.


Quote:
I had been thinking that 2000 minus 4 was 1996. With a 2000 lumen projector I would spread the available contrast (lightest to darkest scenes) over 1996 potential lumens. Whereas, on a 1000 lumen projector, I would have only 998 lumens to spread across the spectrum of scenes. It's like opening an accordion, all the folds(levels of brightness) get farther apart from each other. If this were true, then the brighter projector would always have more contrast.
That would be true if brighness was arithmetic/linear, but because it's logarithmic, that analogy doesn't hold. In both the brighter and dimmer projectors it is working over the same 500:1 range.


-Tom
 

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Joe,


Don't you have pretty poor light control? In that case your minimum black level will be set by ambient light, not the pj, lowering the actual CR at the screen of a dimmer pj. Perfect situation for making the bright XP21N look good.
 

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Discussion Starter · #11 ·
That definitely sounds like it could be a factor. In really bright scenes the room lights up like an operating room, but during most watching at night I do feel like it remains relatively dark. I watch Rose Red the other night, and in the scene where someone is walking down the stairs in the dark with a flashlight and moving it all around, when they shine it into the camera, it is just like they shined the real light in your eyes. It was actually pretty irritating, but extremely realistic.
 
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