Some people are still being told that 200:1 is all we can see.... - Page 13 - AVS Forum
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post #361 of 505 Old 01-06-2007, 07:26 PM
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Originally Posted by armadillo View Post

wuffzack: Yes, most of the discussion centers around simultaneous vs sequential. To answer the decisive question of what CR would be good, I probably would think that 1,324,517:1 should be plenty for me

Sure! But would your eyes be able to see such a high CR in one scene? Like the moon in the dark sky? (simultaneously or sequentially, whatever you like to call it for this situation)
How do the "avs contrast results" http://www.avsforum.com/avs-vb/showthread.php?t=781060 compare to the eyes capabilities?
Does a high ANSI CR make a picture better? If the eye has a limited CR of 200:1 in "narrow view" (simultaneous) a high ANSI CR of 800:1 should not be visible. If the bright and dark parts are in some distance (sequential) the CR of the display should be higher than the ANSI CR anyway (somewhere between ANSI and ON/OFF).
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post #362 of 505 Old 01-06-2007, 08:28 PM
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wuffzack: You are asking the wrong question. Until a display can present a real life of 10^10, there will always be room for improvement. In my HT, I have large screen in front of me. Although I realize that my limited HVS can only meaningfully resolve 200:1 of wherever on the screen I place my focus, the projector does not know what I am looking at. The limitations we have are that the projector can only give us a limited CR for the entire scene. I want the projector to let me pick a particular subimage and still deliver the same 200:1 to match the capabilities of the HVS. Let us assume a particular scene in a movie has four quadrants and each of them has a CR of 200:1 but spread over a luminance range of 1000:1, then the projector must have at least 1000:1 ANSI to let me appreciate each of the quadrants. As soon as I move to another quadrant, the HVS will rapidly adjust its contrast ratio and let me appreaciate that particular quadrant.

The problem then comes when we have a lot of high-frequency contrast exceeding 200:1. Then even the best display will not help, because I will lose either shadow or brightnes detail, because the HVS simply cannot resolve much more than 200:1.
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post #363 of 505 Old 01-07-2007, 12:05 AM
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Originally Posted by armadillo View Post

......then the projector must have at least 1000:1 ANSI to let me appreciate each of the quadrants.

I think I see what you are saying, however "ANSI" is a specific test, 4x4 white/black squares, no varying luminance levels. I really think you are really referencing the CR performance between ANSI and ON/OFF. ANSI is where the "light spill" has its affect on CR.

wuffzack, I would say that a system with a high ANSI CR will perform better with high APL images and a system with a high ON/OFF CR will perform better with low APL images. This would tend to the assumption that a low ANSI and low ON/OFF would be a poor performer, where a High ANSI and high ON/OFF would be the better performer.

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post #364 of 505 Old 01-07-2007, 03:31 AM - Thread Starter
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I think the main problem is that many people are citing the 200:1 as 'all we can see' when in fact we can see a lot more than that across a scene. Some people who misunderstand the context are also are citing that number as means to say that displays can't do more than that, or we can never see more than that, and that is clearly wrong. Going back to my original post, on two occasions 200:1 has been stated to me as the maximum for both the above examples which is why I posted here in the first place.

We may not be able to see more than 200:1 at a border with a bright light (within our immediate focus) but if that condition doesn't exist we can clearly see more than that. To limit 'what we can see' to just a small area within our field of view doesn't seem a fair way to assess our image capabilities, let alone make a statement about it in that context IMHO. It does seem more likely to be the smallest contrast we can see, and not the largest.

In the Gladiator scene, I can still see the 54FL illumination point whilst looking at darker areas either near it or further away and vice versa. There is no brightness or darkness compression going on and the only difference seems to be focus. The contrast perception appears to remain intact at all times. The 'at a border' 200:1 issue doesn't exist within this scene, so our contrast perception isn't limited to that either.

At least, that's how it seems to me with real images and not ANSI patterns which tend to be closer to creating the 'at a border' limitation.

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post #365 of 505 Old 01-07-2007, 06:50 AM
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Originally Posted by Gary Lightfoot
I think the main problem is that many people are citing the 200:1 as 'all we can see' when in fact we can see a lot more than that across a scene. Some people who misunderstand the context are also are citing that number as means to say that displays can't do more than that, or we can never see more than that, and that is clearly wrong.

No, nobody is saying that. What some us are saying is that this limit applies to our field of view at any one instant. If the light level of the scene or our view changes, we can adapt and see luminances over a range of at least 10^10, but our eyes need time to do that. That's why we are blinded by light in a dark environment and require a long time to adjust back to the dark-adapted state. In intermediate lighting conditions, adaptation can be quite quick and takes less than a second. Undortunately, this is thought by others in this thread to mean that it is instantaneous. But it isn't, it's just quick.

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We may not be able to see more than 200:1 at a border with a bright light (within our immediate focus) but if that condition doesn't exist we can clearly see more than that. To limit 'what we can see' to just a small area within our field of view doesn't seem a fair way to assess our image capabilities, let alone make a statement about it in that context IMHO. It does seem more likely to be the smallest contrast we can see, and not the largest.

The question is not whether we can see a bright spot in the corner of an otherwise dark scene. Yes, we can. But we will not be able to know just how bright that spot is. If that spot has shades of different brightnesses, you won't be able to resolve them either. All you know is that "something bright" is there. The reason is that your visual system is adjusted to a different range of contrast. So if that bright spot is 500x brighter than the rest of scene, you will not be able to tell that it 500x. A 400x brighter spot would give you the same sensation of "something bright".
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post #366 of 505 Old 01-07-2007, 06:54 AM
 
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http://archive.avsforum.com/avs-vb/s...0&pagenumber=2

In the archived AVS thread above forum member 'Dave W' IMO actually understands this very subject quite well. I also included the quote from 'Robert' to illustrate why video at it's best is no greater than 200:1, coupled with the fact it's linear vs logarithmic. In fact the thesis I linked by Matthew Trentacoste will explain in detail it is not possible to represent HDR contrast on the order 1000:1 with video gamma, in fact a linear 200:1 is the MAX

http://www.cs.ubc.ca/grads/resources...te_Matthew.pdf

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At any given moment, the eye has a dynamic range of about four decades (10000:1)

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This subject is not in my area of expertise, but I believe that number includes the full iris range.
Since iris ranges from about 7mm max diameter to 1-2mm min diameter, that gives, oh, say 5 f-stops, give or take. So dividing 10000 by 32 (2^5), we get around 300 or so for the contrast ratio of the eye at any given iris position. So using 100:1 is too low of a number.

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See, this is where I have trouble with all of this. So film has a 200:1 contrast ratio? And my DLP projector has a 2000:1 contrast ratio.
But film looks so much better in dark scenes (black level, shadow detail, etc) than my home theater image, even though my home theater image supposedly has ten times greater contrast ratio. I don't get it?

Seeing is believing right, FWIW this is what I explained earlier i.e. film has a log density for latitude or dynamic range, and is why film is digitized into 10-bit or better log format, so to preserve the films dynamic range.
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post #367 of 505 Old 01-07-2007, 08:31 AM - Thread Starter
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Originally Posted by armadillo View Post

No, nobody is saying that. What some us are saying is that this limit applies to our field of view at any one instant. If the light level of the scene or our view changes, we can adapt and see luminances over a range of at least 10^10, but our eyes need time to do that. That's why we are blinded by light in a dark environment and require a long time to adjust back to the dark-adapted state. In intermediate lighting conditions, adaptation can be quite quick and takes less than a second. Undortunately, this is thought by others in this thread to mean that it is instantaneous. But it isn't, it's just quick.

I don't think I was clear - with reference to my original post, I have been told by someone that 200:1 is all a projector can do, and any other number is marketing BS, and another time face to face, that 200:1 is all we can see, so CR numbers are meaningless (and marketing BS). In both cases they had misunderstood what they had been told at a training course (one was on another forum, and the other was in conversation). I have since corresponded with the source (where those people had 'learned' that info) and it was confirmed those assumptions were wrong. See my later posts along with some of Chris's related posts (Poynton was the reference I believe).

Iris adaption is something else, and part of the 'elevator' phenomenom of moving the range we can see up or down within the total range we can see. In this case with this scene, there is no iris adaption, since the light isn't bright enough in relation to the rest of the scene. If it was, the darker parts would disappear, and they didn't.

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Originally Posted by armadillo View Post


The question is not whether we can see a bright spot in the corner of an otherwise dark scene. Yes, we can. But we will not be able to know just how bright that spot is. If that spot has shades of different brightnesses, you won't be able to resolve them either. All you know is that "something bright" is there. The reason is that your visual system is adjusted to a different range of contrast. So if that bright spot is 500x brighter than the rest of scene, you will not be able to tell that it 500x. A 400x brighter spot would give you the same sensation of "something bright".

That's like saying that if something is out of focus, does it stop being something? I don't think it does, I think it remains exactly what it is when we see it directly in focus in front of us. The brightness doesn't change, because if it did, we would perceive it since it's still in our peripheral vision.

EDIT: Changed 'theory' to phenomenon.

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post #368 of 505 Old 01-07-2007, 09:37 AM
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Originally Posted by Gary Lightfoot View Post

Iris adaption is something else, and part of the 'elevator' theory of moving the range we can see up or down within the total range we can see. In this case with this scene, there is no iris adaption, since the light isn't bright enough in relation to the rest of the scene. If it was, the darker parts would disappear, and they didn't.
Gary

Iris adaptation is only part of the mechanisms that ultimately control contrast adaptation. Additionally, there biochemical events (primarily calcium-dependent regulation of a molecule called Calmodulin and retinal interneurons adjusting lateral inhibition of receptive fields). But the sum of all these mechanisms indeed produces the elevator phenomenon (it's not a theory, it's proven). So what we are in fact discussing here is the height of the elevator cabin and that is IMHO ~200:1.

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That's like saying that if something is out of focus, does it stop being something? I don't think it does, I think it remains exactly what it is when we see it directly in focus in front of us. The brightness doesn't change, because if it did, we would perceive it since it's still in our peripheral vision.

Yes, it is there, but you won't be able to tell it apart from something that is less bright or something that has contrast. So if you watch a movie, say StarWars, and you have a dimly light face against a window into space on the left hand side of the screen and a brighly lit spaceship enters the scene on the right, you will perceive that some light comes into your peripheral vision. You won't be able to tell whether it's a spaceship or a planet until you move your fovea there.

So if you now ask whether it makes difference which projector will give you a better experience, IMHO it would not make any difference whether you were watching that scene with 300:1 CR vs a projector that does 20,000:1. Both will give you roughly the same impression of something bright entering the scene. However, as soon as you direct your attention to the spaceship, it will make a whopping difference.
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post #369 of 505 Old 01-07-2007, 09:47 AM
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Gary and armadillo, I think you are both basically right.

One way to express this is the eye's range is like a "pan and scan" with the window somewhere in the 200:1 (plus or minus) range.

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The question is not whether we can see a bright spot in the corner of an otherwise dark scene. Yes, we can. But we will not be able to know just how bright that spot is. If that spot has shades of different brightnesses, you won't be able to resolve them either.....

I don't see this as the real issue here. While it can affect what you see, the eye will adjust to the bright light if the spot is big enough. My main focus in this topic has always been the adaptation to the inverse, a dark spot in an otherwise bright scene.

As this applies to home theater, if the overall average level of light coming off the screen, sitting 12' from the screen, is more than 200 times that of some of the dark details, you will most likely not be able to see those darker details until you lower the amount of light reaching the eye.

This could also be an issue that changes due to screen size. If one half of the screen is 100IRE white and the other half is 0IRE (black), with a small 1IRE (1%) square, 100 to 0 CR = 200:1, you might be able to see the 1IRE square on a 60" screen but not on a 120" screen. The amount of affect, light reaching the eye, can be dynamic, changing with the % field of view the light source occupies.

This topic has "specific" situations where it is valid, not all inclusive.

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post #370 of 505 Old 01-07-2007, 09:58 AM
 
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Chris, this is very easy to explain. In situations, like the Mits. DLP with a gray interior and to a lesser extent the Mits 65813, ambient light enters the screen illuminates the cabinet and can significantly raise the black level needed to see the detail. Secondly, an illuminated screen, from the image, has some reflection back into the cabinet. If the cabinet cannot absorb all of the light it can reflect back onto the screen causing cross contamination and reduce the ability of the TV to hold black levels. It is very similar to front projection, do you want black walls or white, gray or some other reflective surface covering in the room?

The lining doesn't change what is coming out of the lens, it just improves what you can see. It does work, but not on all displays. I have talked a few customers out of the modification because I felt the potential results were not worth the effort/money, nothing to visibly gain.

Okay, but do you see why I asked this fairly simple question? What I was attempting to elicit is an explanation that illustrates precisely why higher simultaneous contrast ratios still provide benefit. Lining the internal cabinet of an RPTV or using a FP in an all-flat black room improves the simultaneous CR of the display system. This improvement is only relevant because we can see this improvement. If it provided no visual improvement, nobody would bother doing these things and likely you would not bother to offer this service to your clients. To the contrary of course, improving the ANSI CR performance of a display does lead to visible improvements in the image. That is why LC CRTs are preferred over AC CRTs, etc. If humans could only see 200:1, or 100:1, or 150:1, or 130:1, or 300:1, or whatever completely unsubstantiated number you want to choose that have suggested errantly in this thread, then doing such things as lining the internals of RPTVs would provide little or no improvement in the image because the simultaneous CR performance of that display would already likely exceed our visual capabilities(depending).

The very services you offer and the very explanation you provide for them quickly disprove the silly nonsense that we can only see CRs as low as the various claims in this thread.
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post #371 of 505 Old 01-07-2007, 10:06 AM
 
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Originally Posted by armadillo View Post

This is ridiculous. With the forum being slow as molasses, I'm not going to quote the many posts I made in which I have said the very same thing. I have always contended that a large immersive image will benefit from high CR. What I have also always said was that you cannot see all of the high CR simultaneously. Go read my posts if you don't believe me.


Your first post in this thread stated the following:

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From reading through a couple of the papers cited in the above link, I would supect that for a 24 FPS movie, 300:1 contrast is more than ample and a higher contrast ratio would not be noticeable; from one paper it would seem that even ~100:1 is pushing it).

You also said this shortly after:

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In order for you to adjust your eyes to different contrast levels, i.e. in order to be able to shift the contrast range of 100-300:1 over the 9 orders of magnitude light intensities you so fervently advocate, you actually do need several seconds. I am not going to argue with you about this, because I have read your previous posts and I don't see you change your mind. But I would suggest that you read some of the papers, because they give you some perspective on human physiology and the neuronal processing of visual signals under laboratory conditions.

Which seems to indicate that a person has a limited contrast range ability in a single scene to the range of 100:1-300:1, and that it takes "several seconds" to adapt that range, i.e. move that range around a much larger range. Of course, your assertions about what the papers said proved to be fully incorrect because everything you cited fully supports what I've been saying if what you cited even had any meaningful relevance at all which they mostly did not.

Do you care to change those statements? Because what you're saying now does not seem to agree with what you previously characterized. That's a positive thing, because you were in error previously, but to pretend that you weren't trying to assert different things previously is somewhat off-putting.
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post #372 of 505 Old 01-07-2007, 10:13 AM
 
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Originally Posted by GlenC View Post

Chris, unfortunately, everyone on this thread has acknowledged that the eye can see CR in excess of 1000:1 or whatever on a given screen with a low enough APL. They have also agreed when looking at a significantly bright area on the screen that the ability to see CR in excess of 200-300:1 is limited when close to the bright area.

The squares test above is simple, looking at the pattern with the large white area, you cannot see all of the squares. When you move something in front of the white area (blocking it from your field of view) you can then see the gray squares. Pretty simple and to the point and it is measurable.

There are a lot of variable situations here and most all are valid, you seem to be the only one that thinks only your view is correct or relevant.

Many of us have actually seen what we are describing and yet you say we don't understand and are wrong. Then you say it is irrelevant or of no interest to you. Sounds like an insatiable need to be absolutely right without exception.

Really? That makes me wonder if you read the thread and the various people repeatedly asserting that we can only see 100:1, or 300:1, or 130:1, or 250:1 or 200:1(pick your number, they come from thin air it seems) in a scene or at any one time. Did you totally miss the dozens of times these things were asserted?

The entire point of this thread was begun with the claim that we cannot see more than 200:1 across a scene. I've been tirelessly rejecting that idea for the last 13 pages. And now all of a sudden everyone wants to pretend that that's not what they really meant?

What I said was irrelevant was sequential contrast issues. That has not been pertinent to the thread since the very beginning because over time we can see a much larger range. That has never been in debate really. You continually have brought that up, however, which is somewhat frustrating because it(being a longer temporal issue) really is not relevant.
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post #373 of 505 Old 01-07-2007, 10:19 AM
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Chris: Please stop misrepresenting what I said. In the first post post, I simply stated that 300:1 is the simultaneous CR we can discern at any instant. This still holds true. If I watch a full frame scene from a distance that allows me to have the entire scene in my fovea, then the CR of the display projecting the image won't make a significant difference. I still maintain that stance. As to the kinetics of adaptation, they can be variable anywhere between 20 ms to 20 min, depending on what luminance levels you adjust to. To fully dark adapt, you need minutes, to fully bright-light adapt, you require a few seconds, and for intermediate luminances it can happen in the sub-second range (that's biology, biochemistry, and muscle (iris) physiology for you). So I have nothing to retract. No departure from what I've been saying. But I will admit that along the way of this thread I have learned a lot and I have been able to better qualify and quantify what my original suspicions were. Let's hear from you whether you have learned something as well...
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post #374 of 505 Old 01-07-2007, 10:23 AM
 
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Originally Posted by armadillo View Post

No, nobody is saying that. What some us are saying is that this limit applies to our field of view at any one instant. If the light level of the scene or our view changes, we can adapt and see luminances over a range of at least 10^10, but our eyes need time to do that. That's why we are blinded by light in a dark environment and require a long time to adjust back to the dark-adapted state. In intermediate lighting conditions, adaptation can be quite quick and takes less than a second. Undortunately, this is thought by others in this thread to mean that it is instantaneous. But it isn't, it's just quick.

Really? Nobody was saying that? You were certainly among those saying precisely that. You said that a display with a CR beyond 300:1 or even 100:1 was not necessary. I don't know how else to interpret that kind of a statement. Even Tom Stites from JVC was trying to assert this kind of claim. Well it's wrong, it's always been wrong, and it continues to be wrong. I've said that from the very beginning of this thread. There has been absolutely no substantiation of those claims that we can only see this much across a scene, despite tireless attempts by yourself and others to support just such claims.

You realize I was the first person in the thread to cite Vos's 150:1 CR limit for *at* a high contrast boundary. I brought that up in the first place because I knew people were going to latch on to some small figure like the limit at a boundary and ignorantly try to claim that that applied to the whole scene. Well, of course, that's exactly what everyone has been doing for a dozen pages.


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The question is not whether we can see a bright spot in the corner of an otherwise dark scene. Yes, we can. But we will not be able to know just how bright that spot is. If that spot has shades of different brightnesses, you won't be able to resolve them either. All you know is that "something bright" is there. The reason is that your visual system is adjusted to a different range of contrast. So if that bright spot is 500x brighter than the rest of scene, you will not be able to tell that it 500x. A 400x brighter spot would give you the same sensation of "something bright".

And that is yet another question. And I strongly disagree with you. As do the various HDR papers that have been cited repeatedly in this thread. We may have difficulty discerning small changes in luminance in a very bright small object in a scene or image if the rest of the scene is relatively dark and we're more generally adapted to the darker setting, however we are very much affected by how bright that object is overall. If it is 500x brighter, or 1000x brighter than the rest of the scene, that is definitely going to have an affect on how we view that object and the scene. There can be added glare and fatigue issues, etc, as described in the HDR papers.
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post #375 of 505 Old 01-07-2007, 10:30 AM
 
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Originally Posted by armadillo View Post

Chris: Please stop misrepresenting what I said. In the first post post, I simply stated that 300:1 is the simultaneous CR we can discern at any instant. This still holds true. If I watch a full frame scene from a distance that allows me to have the entire scene in my fovea, then the CR of the display projecting the image won't make a significant difference. I still maintain that stance. As to the kinetics of adaptation, they can be variable anywhere between 20 ms to 20 min, depending on what luminance levels you adjust to. To fully dark adapt, you need minutes, to fully bright-light adapt, you require a few seconds, and for intermediate luminances it can happen in the sub-second range (that's biology, biochemistry, and muscle (iris) physiology for you). So I have nothing to retract. No departure from what I've been saying. But I will admit that along the way of this thread I have learned a lot and I have been able to better qualify and quantify what my original suspicions were. Let's hear from you whether you have learned something as well...

I'm just quoting what you said. You still latch on to the 300:1 figure, and I've asked you repeatedly where that number comes from, but you've not supported that figure in any way. When Poynton cited a figure of 1,000:1 across a scene, you rejected that figure. This seems to indicate to me that you think we can only see 300:1 across a scene.

My point is that you can easily see many orders of magnitude simultaneously in a single scene. The figure I cited was 100,000:1, or 5 orders of magnitude as a maximum capability. You and others reject that an instead cling to much lower numbers on the order of 2 orders of magnitude, such as this 300:1 number.

I'm glad I'm at least making progress in convincing you that the claim that we can only see somethhing on the order of 300:1 in a single scene is ridiculous, even if it involves pretending you didn't mean what you said.
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post #376 of 505 Old 01-07-2007, 10:33 AM
 
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Originally Posted by armadillo View Post

Chris: I wished you would read my posts so I wouldn't have to repeat myself. There are two ways of masking the white square if it is already present. I can put my hand in front of it or I can move my fovea so that less of bright square is in the center. That will lead to adaptation and the faint square reappears in my HVS (although it was present on the screen all along).

Yes, my question was which method are you using? These are two RADICALLY different methods and lead to two VERY different kinds of conclusions.
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post #377 of 505 Old 01-07-2007, 10:34 AM
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Chris: The various numbers are not surprising, because we are all human beings with individual CR perception. The 130 number I threw in came from contrast sensitivity experiment cited earlier (those were done at constant luminance). You jumped all over that post and I then gave you a link that contrast sensitivity also applies to luminance (post #238; http://www.avsforum.com/avs-vb/showt...59#post9342459). Just because we are using different numbers, does not discredit the findings, because different individuals under investigation may have different sensitivities (get over it). You still owe us a scientific reference that supports your contentions. But I now see that you no longer want to consider simultaneous vs sequential contrasts. Please state for the record what you believe is the simultaneous CR of the HVS. I will state for the record that I'm convinced it is 100-300:1.
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post #378 of 505 Old 01-07-2007, 10:45 AM
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Originally Posted by ChrisWiggles View Post

Yes, my question was which method are you using? These are two RADICALLY different methods and lead to two VERY different kinds of conclusions.

Both methods work for me
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Originally Posted by armadillo View Post

Chris: The various numbers are not surprising, because we are all human beings with individual CR perception. The 130 number I threw in came from contrast sensitivity experiment cited earlier (those were done at constant luminance). You jumped all over that post and I then gave you a link that contrast sensitivity also applies to luminance (post #238; http://www.avsforum.com/avs-vb/showt...59#post9342459). Just because we are using different numbers, does not discredit the findings, because different individuals under investigation may have different sensitivities (get over it). You still owe us a scientific reference that supports your contentions. But I now see that you no longer want to consider simultaneous vs sequential contrasts. Please state for the record what you believe is the simultaneous CR of the HVS. I will state for the record that I'm convinced it is 100-300:1.

The various numbers are surprising because people are asserting them as factual. They are completely unsupported. Not a single paper mentions these numbers at all in this manner. The 130:1 number was interpretive error on your part, and has in my mind been completely rejected. Of course it has to do with luminace differentiation. That's what CSF is interested in. That does not make it relevant to this discussion.

My reference was the papers from Brightside. That is 5 orders of magnitude simultaneously in a scene. It's quite simple.

I will even quote myself, see post #7 in this thread:
Quote:


Our iris adjusts relatively slowly, at at any one iris position we can see about 100,000:1 across a scene. This is, obviously, significantly greater than the 100:1 or 200:1 numbers so often erroneously quoted. If humans could only see 100:1 or 200:1 instantaneously, we wouldn't hardly be able to drive around at night! With iris adjustment over time, it's more like 10^14:1.

Or post #10 in this thread:
Quote:


A very common experience we all have frequently in real life (except in Seatte ) is being indoors and looking outside on a sunny day. The CR of a scene like that can easily be 100,000:1, and yet we have no difficulty seeing details in the darker interior room, and outside simultaneously with little or no iris adjustment. According to many people who are loosely repeating numbers that float around, this would be impossible! Yet billions of people across the world have no difficulty seeing when encountering these kinds of very normal situations. Some people with degenerative eye diseases or other problems can end up with very serious reductions in the ability to see contrast in an image and end up with numbers as low as you describe, but this seriously impacts their ability to function in the world. For instance they would be prohibited form doing things like driving or operating machinery...


Or post #12:
Quote:


It's just commonly held belief that we can only see a hundred to one, or a couple hundred to one or so, and this gets spread around and pretty soon reputable people start saying it, and by that time of course it becomes FACT and then it ends up getting taught as fact. A few minutes of simple testing and measuring can very quickly disprove this. In fact, I'm quite surprised that Tom is stating these things, because he should be able to measure and test his own vision quite quickly and easily on a checkerboard pattern and see how much he really can see. An easy way to do this is to throw up a checkerboard pattern (he can measure the ANSI, or a lay person can go by the rough ANSI measure of their projector), and then put his hand in a black square and see if he can see a shadow of his hand. If the projector's ANSI is up towards 300:1 (or whatever number you think is the maximum we can see) then presumably the projector is exceeding what we can see and so there is no way that we could see a shadow in the black square. Impossible(the claim is). Try it and see what happens.

I more fully expanded this in post #19:
Quote:


The more direct source is from conversations Darin and I had with the folks at Brightside. At the time we were fighting the same misconceptions here on the forum about how little we could see instantaneously. At that time the popular number was 100:1, so at the very least it's nice to see the claims have creeped up to 200:1 or 300:1 or so, which we presented to the guys at Brightside who laughed at that idea. They quoted 100,000:1 instantaneous (5 orders of magnitude), and roughly 10^14:1 over time with full iris adaptation.

The closest text-source they have which mentions this is found here:

http://www.brightsidetech.com/tech/p...ggraph2004.pdf

See section 3.

Excerpt:

Quote:


The eye can capture approximately 5 orders of magnitude
of dynamic range effectively simultaneously. No conventional display
technology comes close to this. Yet, there are limitations to
this capability as described below.

3.1 Local Contrast Perception
While we can see a vast dynamic range across a scene, we are unable
to see more than a small portion of it in small regions (corresponding
to small angles). Different researchers report different
values for the threshold past which we cannot make out high
contrast boundaries, but most agree that the maximum perceivable
contrast is somewhere around 150 : 1 [Vos 1984]. Scene contrast
boundaries above this threshold appear blurry and indistinct, and
the eye is unable to judge the relative magnitudes of the adjacent
regions.

Their HDR display has enormous on/off CR, and significantly greater dynamic range than any conventional display. In addition, they achieve something like 25,000:1 ANSI contrast (yes that's ANSI, not on/off).

If you google for "disability glare" you can find a variety of sources to journal articles that discuss the reduced CR range that we can see right at a high contrast boundary. This is important in real life, it's why stop lights have those big black borders around them, and why the entrance of a tunnel is lit more brightly than deeper into the tunnel for example, things which you'll find discussed in these studies.

Also, you can google for 'contrast sensitivity function' which is another source of confusion about the specific 100:1 number. CSF does not have to do with contrast range between black and white, instead it has to do with the Just Noticeable Difference, essentially bit-depth requirements to avoid visible banding. But some apparently have confused that and the 1.01:1 or 1:100 expression (1% JND) into a maximum visible CR range of 100:1 which of course is a completely erroneous interpretation.

This has been my position from the very beginning. It's farily well laid out, in my opinion. I feel as if I've been fairly clear and reasonably thorough in my position. I don't feel as if I need to repeat myself again here for you, you can just read all my above quotes which I posted earlier in this thread.
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Chris: I give up.
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Chris: I give up.

Thank goodness.
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Chris, you have continually fixated on your perception of the topic of this thread.
Quote:


The entire point of this thread was begun with the claim that we cannot see more than 200:1 across a scene.

You assumed that "across a scene" was the only way to look at the issue. That is not the issue and every one in here agrees that you can easily see very high contrast ratios across a scene, given a moderate APL.

I will ask a simple question. If you look at a full white field (100 IRE, say 15fL), you contend that you can distinguish between small objects in that field having CR of 500:1, 700:1, 1000:1 and/or possibly more, is this true?

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Originally Posted by armadillo View Post

Chris: I give up.

Feel like you have been kicking a dead horse trying to get it to run?

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post #384 of 505 Old 01-07-2007, 12:33 PM
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Feel like you have been kicking a dead horse trying to get it to run?

Running is out of the question, but may be budge an inch?
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Quote:
Originally Posted by GlenC View Post

Chris, you have continually fixated on your perception of the topic of this thread. You assumed that "across a scene" was the only way to look at the issue. That is not the issue and every one in here agrees that you can easily see very high contrast ratios across a scene, given a moderate APL.

I will ask a simple question. If you look at a full white field (100 IRE, say 15fL), you contend that you can distinguish between small objects in that field having CR of 500:1, 700:1, 1000:1 and/or possibly more, is this true?

I am unclear as to what I'm supposed to be looking at. It it's a white field, I'm just looking at an all-white field. But regardless, yes we can see in a single view across a single image or scene CRs well above 1,000:1. As such, displays with simultaneous CR(such as ANSI CR) limits below this do not exceed our capabiliites and as such leave significant room for improvement. In the above, I cited the figure of 5 orders of magnitude, which is more intuitively correct and backed by several of the HDR papers cited. Poynton cites 1,000:1, but I don't feel he is the best source in this regards, which is what I've explained previously. Joel Silver at the ISF, in turn, cites Poynton's 1,000:1 figure. Even if you go with the much much lower 1000:1 figure, that is not insignificantly larger than the piddling few hundred:1 figures cited here (and by all means if you can explain where all the various versions of those figures come from, I'm all ears. It seems to me people are just making them up though because they aren't cited anywhere, or as was certainly the case at least in one instance with 'armadillo's' 130:1 figure, drawn from a mistaken/ignorant interpretation of CSF which unfortunately seems to be a continuing pattern in these discussions...)

The only display device I am aware of that can really exceed our capabilities in these regards, as I mentioned before, is the Brightside display. It achieves an ANSI CR spec'd at 25,000:1. If you expect a regular consumer display with a few hundred to one ANSI to come close to exceeding our visual capabilities in this regard, you are seriously mistaken. However, I am still struggling to understand what exactly your position is on the matter because you continue to revert back to temporal issues such as on/off CR. Clearly you do understand that ANSI CR performance in current displays is a limitation, given your cabinet-lining services which go hand-in-hand with this understanding.

Anyway, I'm not sure why you asked me to state this yet again, as I just above stated this again, and I've been saying the same thing over and over and over since the very start of the thread. I don't know what you hope to achieve by having me rearticulate the same position a dozen different ways. Post #379 contains all this, you could just read that post if you wanted.
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I also was curious as to what some of the relevant textbooks said about this(other than Poynton), I have a few on order which I will pick up shortly, so I'll report back what they have to say, if anything. I'd be interesting to see what the figures there are.
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Quote:


That is not the issue and every one in here agrees that you can easily see very high contrast ratios across a scene

Really?

In my count, we have to some degree or another, some claims that we are limited to a few hundred to one at one time, i.e. in a single scene: tstites, armadillo, yourself, and houston. Some of those claims appear to be strongly contradictory, especially yours, armadillos, and houston's. (to be fair I discount tbrunet's posts entirely)

Other than myself, Darin, Gary(and some others who made a few sporadic posts here), and the various scientific papers cited (including Matthew's and his posts) there seems to be a significant pattern of thinking among the others I mentioned who do indeed feel that we have severe limitations across a single view on the order of a hundred or a few hundred to one CR. That mistaken understanding was why Gary started the thread in the first place(under the claim that it seemed the ISF was also propagating this erroneous thinking), and that's the same mistaken understanding I continue to try to correct.
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Originally Posted by ChrisWiggles View Post

I am unclear as to what I'm supposed to be looking at.

Pretty much says it all. You can lead a horse to water, but you can't make it drink..................

This is is about as basic as it gets and easy to follow, go into a dark room, shine a flashlight into your eyes and tell us how much detail you see in the room, with the flashlight shining into your eyes. Next, turn off the flashlight, how long before you see the room details? This is simple , a 10-year old can do it

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post #389 of 505 Old 01-07-2007, 01:40 PM
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Quote:
Originally Posted by armadillo View Post

The 130 number I threw in came from contrast sensitivity experiment cited earlier (those were done at constant luminance). You jumped all over that post and I then gave you a link that contrast sensitivity also applies to luminance (post #238; http://www.avsforum.com/avs-vb/showt...59#post9342459).

Do you understand what a reciprocal is? If so, why do you bring up CSF as if it has something to do with the maximum CR a person can see? How fast a car can take off and how fast it can stop both relate to acceleration, but that doesn't mean that one tells you about the other. Just because testing the lowest CR a person can see is about luminance and so is testing the highest CR, that doesn't mean one gives you an idea of the other.
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Originally Posted by GlenC View Post

At that, my tale on this topic is that on a full white field you should be able to see the difference in a small black square that is part .04fL and .03fL, but not .03fL and .02fL. ff the screen was at 16fL, then the three levels of black would be .08, .07 and .06fL.

These numbers look wrong as you are using different ratios. That is, if it is .04, .03, and .02 then double that would be .08, .06 and .04.
Quote:
Originally Posted by GlenC View Post

As this applies to home theater, if the overall average level of light coming off the screen, sitting 12' from the screen, is more than 200 times that of some of the dark details, you will most likely not be able to see those darker details until you lower the amount of light reaching the eye.

It seems like you just arbitrarily decided to move to an average level being 200 times? Since CRs are generally done from the average for the scene divided by the lowest value, where did that come from. It looks like an attempt to find a way to justify the 200:1? Have you done any testing of that or seen anything that says the 200:1 claim is from the average and not the peak?
Quote:
Originally Posted by Gary Lightfoot View Post

Some people who misunderstand the context are also are citing that number as means to say that displays can't do more than that, or we can never see more than that, and that is clearly wrong. Going back to my original post, on two occasions 200:1 has been stated to me as the maximum for both the above examples which is why I posted here in the first place.

In my experience, I don't think it is just that people who attend ISF courses are misunderstanding what is being stated. I had somebody who teaches these courses make this statement about 300:1 (or something like that) to me. We talked about it a while and hopefully he went and did some of the testing I suggested.

--Darin

This is the AV Science Forum. Please don't be gullible and please do remember the saying, "Fool me once, shame on you. Fool me twice, shame on me."
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post #390 of 505 Old 01-07-2007, 01:53 PM
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Glen: You are so full of it. That is completely irrelevant in this context. The HVS can resolve CR far in excess of 100,000:1. How am I doing Chris? feel free to quote me on that if anyone should give you more trouble.
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