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Some people are still being told that 200:1 is all we can see.... - Page 6

post #151 of 505
Quote:
Originally Posted by armadillo View Post

Chris. You are hopeless. Your test means nothing, because it isn't fast enough. Your visual system starts to adapt immediately, particularly when you are focusing on the area where the shadow is. So if you did the test while looking at the right edge of the screen and then someone would wave the hand on the left edge for less than a second, I predict that you'd see no shadow at all. In fact, I would predict that if someone moved the laser pointer quickly across the screen, you wouldn't be able to see it either (why do you think that some people have problems following speakers who jerk the laser pointer around in presentations?). However, as soon as something lingers for a second or two, your visual system would adapt. So the ideal test would be having someone quickly move a laser and a dark shadow in different areas of the screen simultaneously. I bet you would sit there and ask whether the event had occurred, let alone resolved and compared the contrast.

Do the test. It doesn't concern me if or how the visual system quickly adjusts chemically or otherwise as you move your eyes around.

I am slightly tired of juvenile poo-pooing by people who aren't willing to do a simple test and instead want to pull the discussion away from the topic of interest. If you can see beyond the ANSI CR capability of current displays, no matter how you do it, then that means that current displays can be improved. Whether you can see this with fast adaptation or not is immaterial. We can see it in a single scene. Period.

Did you bother to read the link you posted?

This thread is turning into attack of the newbies.
post #152 of 505
Quote:


I would be curious if darinp2, ChrisWiggles, tstites, and HoustonHoyaFan can agree with all of these points:

1. The HSV may only be able to distinguish ~200:1 contrast across an arbitrarily small angle (e.g. adjacent pixels)
2. Regardless of #1, intraframe contrast would need to be far in excess of this amount, and probably in well in excess of 10,000:1 in order for further improvements to be imperceptible in all scenes
3. Therefore, point #1 (which is what HoustonHoyaFan is going on and on about) has no bearing whatsoever on any currently available front projector, in the sense that no front projector comes close to reaching the limits of the HSV, even in a single frame, and thus anyone who quotes this 200:1 number as a justification for any current specifications is entirely misguided.

I agree with these points, which is what I've been saying the entire thread. I summarized simplistically in post #104:

1) We can see about 5 orders of magnitude in a single scene, or 100,000:1
2) This means that ANSI CR contrast performance that is significantly less than that cited in #1 is above our visibility threshold and does not exceed the capabilities of our vision, generally.

From these two points of view which I hold (accurately or not), I can say that ANSI CR performance of say 500:1 does not exceed our visual capability and there is room for improvement which could be detected by human viewers viewing that scene at a relatively normal viewing ratio that we encounter in most home-theater viewing environments.


Quote:


Let's suppose we have a display with four vertical columns, which from left to right are called A, B, C, D. The left column, A, is very dark, but not quite black. The second column, B, is 100 times brighter than A. Similarly, C is 100 times brighter than B, and D is 100 times brighter than C. Therefore, column D is one million times brighter than column A. The question is: if you looked at this display, could you perceive all four columns as distinct? There are two ways to answer the question. One way is to allow the viewer to move his eye. In this case, it is obvious that all four columns would be easily distinguishable; and in fact, column A would probably be distinguishable from black. Given that screens are large and that in a semi-static scene a viewer is easily able to move his eyes around the screen, it is obviously necessary to allow such large contrast ratios within a given frame -- and that should be the end of the discussion. However, even if we impose the unrealistic requirement that the viewer not be allowed to move his eyes, I still contend that all four columns would be simulateneously distinguishable. And if all four columns are distinguishable (as opposed to 3) then we know we're viewing more than 10,000:1 contrast *at the same time*.

However I do not agree that we have this much capability, based on what I've read and experienced. 1 million to one in a single scene is unlikely if the presence of the brightest white is still within your field of view in a significant way such that you are more adjusted to that white level. A million to one is an order of magnitude larger than the 100,000:1 figure which is the largest figure, from Brightside.
post #153 of 505
Quote:
Originally Posted by darinp2 View Post

I don't think "per visual frame" and limits between adjacent pixels or adjacent spots on the retina are the same thing, since a visual frame can include tons of pixels and tons of spots on the retina and there can be multiple transitions within a visual frame. It seems like your claim is more "per transition per visual frame" or something like that and not the total per visual frame, but I'm still not 100% sure.

That's it, as I see it, and as I posted previously, so the CR <300 is per edge (perhaps ledge is a better term), not per frame. There may be many sharp "luminance ledges" in a frame, so we may need 300:1 at a wide range of luminances, which may require 1000's to 1 CR PER FRAME (non-adjacent spot measurements to get this CR) to achieve 300:1 at various luminances, eyes moving or not.
post #154 of 505
Quote:
Originally Posted by ChrisWiggles View Post

That's exactly my point. It is only correct when applied to edges, extremely localized ... The claim that is at issue is basically a claim that ANSI CR beyond say 200:1 is unnecessary because it exceeds our visual capability. That claim is nonsense.

I don't see how anyone could argue against this.
post #155 of 505
Quote:
Originally Posted by mark_1080p View Post

I don't see how anyone could argue against this.

You and me both.
post #156 of 505
Good -- it seems we're converging on a common understanding here. The important point is that the HSV is not the limiting factor in our perception of front projectors, nor will it be for a considerable time. Furthermore, anyone who claims that a current projector's specifications are "good enough because the HSV can't distinguish any better" is either uninformed or purposely misleading.

Quote:
Originally Posted by ChrisWiggles View Post

However I do not agree that we have this much capability, based on what I've read and experienced. 1 million to one in a single scene is unlikely if the presence of the brightest white is still within your field of view in a significant way such that you are more adjusted to that white level. A million to one is an order of magnitude larger than the 100,000:1 figure which is the largest figure, from Brightside.

I agree with all of that -- but in order for all four columns to be distinguishable in my test scenario, all that is required is the ability to detect contrast ratios in excess of 10,000:1 (and not necessarily 1 million to one). In other words, in order to discern the four columns as distinct, it's not actually necessary to perceive the entirity of the contrast levels. In my example with four columns, there are three contrast jumps (A to B, B to C, and C to D). As long as the HSV can detect more than two of the jumps in their entirity, the four columns can still appear distinct. To elucidate the point further, consider having only two columns, A and B, where B is 100x brighter than A. Now suppose the HSV only could detect contrast ratios of 2:1. Even in this case, A and B would still be distinct, with B appearing brighter than A, despite that B:A >> 2:1.

Incidentally, I thought of perhaps an even better test scenario, which is exactly as I stated before, but instead of four columns arranged from left to right, use four quarters of a circle. This way you could see the intersection of all four sections all at once. Then, stare at the center of the circle, and see whether the four quarters are distinguishable. (Of course, even if they're not, you can still move your eye around so that they would be, which is why in an ideal world, projectors would have million-to-one ANSI contrast ratios). Although we don't have any easy way of constructing such a test, a weaker version could be performed with ease on an HDR display -- and I encourage HoustonHoyaFan, or anyone else who has the resources, to give it a try and let us know the results. I would be extremely surprised if a circle with four quarters whose brightnesses are 1, 20, 400, and 8000 are not simultaneously distinguishable on an HDR display with sufficient dynamic range.
post #157 of 505
Quote:
Originally Posted by tbrunet View Post


Quote:
Originally Posted by scaesare View Post

Originally Posted by scaesare
However when somebody instead responds blindly, often posting out-of-context snippets of articles they they don't even understand all the while dodging the points made, over, and over, and over again, ...

Very low and very high diffuse re ectances, such as 0.01{0.04 for brushed black velvet and 0.93{0.97 for clean new snow rarely form contrasts that exceed 100:1.

http://www.cc.gatech.edu/gvu/animati...s/hicont98.pdf
2.1. Eye movement research
The processing ability of the HVS is limited, and is concentrated within a central area of (the two- to five-degree wide region of the retina centered at the direction of gaze, and both resolution and color sensing ability drops rapidly away from the center of this region) in visual angle, named the Fovea. In order to maintain a temporally and spatially continuous representation of our environment, the HVS must enact eye movements in order to bring the Fovea, and all its processing power, to bear upon important areas of the scene. These eye movements are called saccades and are enacted approximately every 100-500 msecs

thomas

(Psst... Thomas... you need to be more careful having multiple windows open while trying to troll post responses... you just quoted a post of mine a year old from a thread that's been closed... as if I had just said it in this thread.)
post #158 of 505
Quote:
Originally Posted by ChrisWiggles View Post

However I do not agree that we have this much capability, based on what I've read and experienced. 1 million to one in a single scene is unlikely if the presence of the brightest white is still within your field of view in a significant way such that you are more adjusted to that white level. A million to one is an order of magnitude larger than the 100,000:1 figure which is the largest figure, from Brightside.

Ok, folks. Let's just say if we have a projector with On-Off=ANSI=100000:1 we will all be very happy and except for extended blackouts in perfectly dark caves not see any contrast issues.
post #159 of 505
Quote:
Originally Posted by ChrisWiggles View Post

Yes. And the only scientific statements that directly bear on the questions at hand come from the folks at Brightside. And they cite 100,000:1 as the instantaneous CR capability of the human eye across a single scene with no iris adjustment.

Here is a direct challenge Chris.."with no iris adjustments", Brightside made such a statement?... not publicly, they would be laughed at. Whoever says that does no comprehend the dynamic operation of the human eye! Maybe Wikipedia or Lindahl could clear up their confusion
Quote:
Originally Posted by Lindahl View Post

That's just it, though. You are perceiving , but at any given instant, your eye is only seeing 200:1 (or whatever small number). The brain is using iris adjustments (and possibly chemical adjustments, as mentioned in the Wikipedia article) to stitch together an image that you perceive to have a much higher contrast ratio.

Point Wikipedia

**Remember when you look at a scene with a very bright area and a very dark area in it you won't actually be able to see detail in both areas at once. When you look at the dark area your pupil will get larger to let more light in and vice versa when you look at the bright area. Your eye basically adjusts its exposure for what you are looking at continuously. Then with the brain's processing it can make you "think" you can see detail in both at once.
This observation can be explained by the structure of the retina, in which the foveal region responsible for the vision of fine details spans only about 1.7 visual degrees, while the parafoveal vision can span over 160 visual degrees, but has almost no ability to process high frequency information [Wandell 1995]
post #160 of 505
I am waiting for a list of seminal article on HVS contrast from one of the junior researchers. It may take a few days.

Here is a link to a simple test, similar to ones used in development testing of our device.

http://vision.psych.umn.edu/~gellab/...Paper_Kwon.pdf

errata
Earlier I posted this:
Quote:
Originally Posted by HoustonHoyaFan View Post

... levels outside that range are clipped into white and crushed into black.

I have been told that a more precise statement would be; in a context free test, levels above and below the current visual frame's discrimination range (<200:1) would be compressed into the high and low levels respectively.
post #161 of 505
Okay, I'll try again, although I cannot possibly be right given that the PR (post ratio) of Chris vs myself is 1,000:1 I think it is undeniable from the literature that the HVS cannot resolve contrast ratios beyond 300:1 at any given moment. It can, however, adjust this contrast resolution dynamically over an astounding range of luminance of a billion:1 (the real world actually presents itself with such high CR). So as we look at the real world, we can adjust our perception of contrast by moving our foveal region to different "scenes" in the real world. This contrast adaptation occurs over seconds and not instantaneously. Noone says that projected images currently match the real world and it would of course be desirable to approach that. So as the projected images grow larger and resolution increases, we can benefit from higher CR if the projected image extends beyond our foveal area. We can then move the fovea across a large image and our vision will adapt to the contrasts within selected regions of that larger image. So the real issue isn't the ANSI contrast of a single movie frame. The question is how that information is visualized. If you have a small image that can be fully appreciated by the fovea, you won't benefit from a higher CR. If you have a huge image in front of you and you allow the eye to move across that image, taking in "subimages", then each of those subimages will be perceived as an individual subimage with its own CR. Here, a higher CR will certainly be beneficial. But all of this takes time, imposed by the kinetics of biochemical events and neuronal adaptation.
post #162 of 505
Quote:


I think it is undeniable from the literature that the HVS cannot resolve contrast ratios beyond 300:1 at any given moment.

It is very much deniable. You make no qualifications about this ratio or what it means. Also, where is this number coming from? Nobody knows. Does this ratio have to do with small angles i.e. at a boundary? If so, then the way you characterize this figure is grossly inaccurate and misleading. Thanks for trying.
post #163 of 505
Quote:
Originally Posted by HoustonHoyaFan View Post

errata
Earlier I posted this:

I have been told that a more precise statement would be; in a context free test, levels above and below the current visual frame's discrimination range (<200:1) would be compressed into the high and low levels respectively.

This still does not seem to match what you were saying earlier, as this says "visual frame" which I interpret to be a single scene. 200:1 across a single scene is way lower than we can see. At a boundary, things get this low very localized, but across a scene it is much larger. However there may be a different meaning to "the current visual frame" which should be elaborated if that's the case.
post #164 of 505
Chris, you are free to deny whatever you want. Several posts on this thread have given you references of scientific papers that arrive at limited contrast of the HVS in the range of 100-300:1. I am citing from the following links:

1. http://www.cc.gatech.edu/gvu/animati...s/hicont98.pdf
"The huge input range of the human visual system is largely the result of adaptation processes.
As summarized by Walraven and colleagues [36], several researchers have isolated the response of retinal photoreceptors from adaptation e ects by measuring cell responses to very brief flashes of light. Their measurements indicate that without adjustment by adaptation processes, responses vary only in a narrow range of light intensities covering about two factors of ten, or 100:1."

2. http://www.cse.yorku.ca/~wolfgang/papers/hdrwinmgr.pdf
"Furthermore, there is a limit to how much contrast can be perceived in a very small neighbourhood of the visual field. ... The threshold at which this occurs, the maximum perceived contrast, is reported to be around 150:1 [9]."

And yes, this has to do with small angles, because it gets even worse if you leave the foveal area. The black and white patterns you like to cite are irrelevant, because our retina has very limited color vision outside the fovea, because the cones (the color-sensitive photoreceptors) are concentrated there, whereas the rods (luminance detectors) are in the periphery. You simply fail to understand that the HVS has complex spatio-temporal processing that primarily results from adaptive processes within a narrow field of view. The contrast adaptation occurs dynamically as we move the foveal area across limited areas of interest with a huge 3D space. However, within each of these limited areas, the contrast does not exceed 100-300:1. As I said, large, immersive projected images will beenefit from higher CR, but if you look at a small image that is covered by your foveal area, you simply won't be able to resolve more contrast than the numbers the scientific literature gives you. So go ahead and deny, I couldn't care less.
post #165 of 505
Quote:
Originally Posted by HoustonHoyaFan View Post

I am waiting for a list of seminal article on HVS contrast from one of the junior researchers. It may take a few days.

Here is a link to a simple test, similar to ones used in development testing of our device.

http://vision.psych.umn.edu/~gellab/...Paper_Kwon.pdf

What is the point you are trying to get across with that paper? That example shows how a low contrast area can disappear. Which is one of the reasons that high contrast ratio is needed in order to keep certain transitions visible. That is, if they are invisible on a low contrast device and visible on a high contrast device, then that supports that higher contrast ratio showed an improvement as far as keeping details in the images visible. Although this test could also help show how a higher CR projector could show improvement as far as having the transition between the edge of an image that is supposed to be black and a black velvet border of a screen frame be invisible, which is what a projector with perfect CR would achieve. A much lower CR projector would actually have a higher CR at the transition from the screen edge to the border when the image is supposed to be black.

In that example the edges on the right are blurred also. That also goes along with my point about using easier cases if we are truely looking for the most that people can see, as harder cases (like smoothed edges) don't result in the most.
I understand that it is addressing how our eyes adjust and has some good information that way, but I hope the stuff from the junior researcher will address high contrast boundaries in the easiest cases for our eyes for a given range within an image. For instance, small areas of bright and not just large areas of bright.

I would appreciate it if you would ask the junior researcher this one. Considering a black velvet room with a screen with a black velvet border and projecting the following image from William Phelps:
Quote:
Originally Posted by wm View Post


while a piece of black posterboard that blocks 95% of the light is placed over part of the "black" area, a little ways below the white squares at a distance that makes it easiest to see, in the image that is being projected. Then a white laserpointer is pointed one of the lower white squares. Would a person be able to see the dot from the laserpointer, the white square it is pointed at, the "black" from the projector that is actually gray and the "black" on the black posterboard at once (while being at a viewing ratio that makes it easiest to see them) if the levels were:

White laserpointer: Much higher than 20 ft-lamberts
White square: 20 ft-lamberts
"Black" from projector: 0.05 ft-lamberts
Posterboard: 0.0025 ft-lamberts

In the above, the ratio between the transition between the white laserpointer and the white square and the transition between the projected "black" and the posterboard would be 400:1.

The test could be similarly done with vertical lens shift by moving the image down and considering the black velvet screen border instead of the black posterboard. If a person could see all 3 transitions at once, then a projector that could do way more simultaneous CR in that image could be considered and whether the person could then see the transition from the "black" from the projector and the black posterboard or the screen border at the same time as seeing the white laserpointer and the white square.

Thanks,
Darin
post #166 of 505
Quote:
Originally Posted by armadillo View Post

2. http://www.cse.yorku.ca/~wolfgang/papers/hdrwinmgr.pdf
"Furthermore, there is a limit to how much contrast can be perceived in a very small neighbourhood of the visual field. ... The threshold at which this occurs, the maximum perceived contrast, is reported to be around 150:1 [9]."

And yes, this has to do with small angles, because it gets even worse if you leave the foveal area.

Why did you cut out the, "If you separate the spots in space, you will again be able to see their variations in brightness" part?
Quote:
Originally Posted by armadillo View Post

The black and white patterns you like to cite are irrelevant, because our retina has very limited color vision outside the fovea, because the cones (the color-sensitive photoreceptors) are concentrated there, whereas the rods (luminance detectors) are in the periphery.

We don't need color vision to differentiate things in the grayscale, like white and black. Luminance detectors are good for high contrast boundaries. If our limit is 150:1 in a very small area and at the same time even another 2:1 on the left periphery and another 2:1 on the right periphery, the total for the whole frame would be much higher than 150:1. The above makes it look like you think the difference between black and white is their color in the above, when it is the relative luminances that are the important part. Coming from a projector black and white could have identical color balances (like D65), but different luminances.

--Darin
post #167 of 505
I cut it out, because what really matters is to see contrast at boundaries. That's why we want higher resolution displays. That's why some people prefer sharp DLP displays over softer SXRD. If all you do in your HT is watch white squares on a black background, then there is no point in discussing this at all. You (maybe I should say I) want to see contrast at boundaries and I want to see those in color.

Make a quick test. Read this text with your eyes at the closest possible distance. Then try and discern colors and contrasts outside of your foveal area. Can you eveb see the contrast between the browser's window frame and your desktop? Even if you do, how sharp is that?
post #168 of 505
Quote:
Originally Posted by armadillo View Post

I cut it out, because what really matters is to see contrast at boundaries. That's why we want higher resolution displays. That's why some people prefer sharp DLP displays over softer SXRD. If all you do in your HT is watch white squares on a black background, then there is no point in discussing this at all. You (maybe I should say I) want to see contrast at boundaries and I want to see those in color.

Sorry, but I don't think you are even making much sense. Some boundaries are in color and some are not (and you should be able to make out both when they are supposed to be visible), but the center of your vision is the most color sensitive and you can directly look at boundaries that are in color. What we are talking about here is multiple boundaries in the same image (since this is one of the things that displays need to be able to do to maintain visible details). Test patterns help find the limits. We can also use some real images (which I have also talked about elsewhere), but people really should be able to comprehend how testing with patterns relates to what is possible with real images.

That part you cut out is definitely relevant to contrast at boundaries. Not every boundary will be within a few small degrees of your vision and if everything outside that just blurred to the same level then movies would look way different to us than they do. The ability to look at one part while still being able to perceive that there are things outside that area is a very important aspect of our vision. It is one thing that has kept us alive. And perceiving that there are other things out there requires that they have transitions. Especially contrast transitions.

Seriously, do you not care if everything outside that small angle range just blurs to one level, or do you care that some boundaries are maintained as visible outside there too?

--Darin
post #169 of 505
Quote:
Originally Posted by armadillo View Post

Chris, you are free to deny whatever you want. Several posts on this thread have given you references of scientific papers that arrive at limited contrast of the HVS in the range of 100-300:1. I am citing from the following links:

1. http://www.cc.gatech.edu/gvu/animati...s/hicont98.pdf
"The huge input range of the human visual system is largely the result of adaptation processes.
As summarized by Walraven and colleagues [36], several researchers have isolated the response of retinal photoreceptors from adaptation e ects by measuring cell responses to very brief flashes of light. Their measurements indicate that without adjustment by adaptation processes, responses vary only in a narrow range of light intensities covering about two factors of ten, or 100:1."

You expect people to believe you when the precise papers you quote clearly are discussing local contrast perception limits? Your intellectual dishonesty in quoting these papers is staggering.

How about the first sentences in the abstract of this article:

"High contrast images are common in night scenes and other scenes that include dark shadows and bright light sources. These scenes are dicult to display because their contrasts greatly exceed the range of most display devices for images. As a result, the image contrasts are compressed or truncated, obscuring subtle textures and details. Humans view and understand high contrast scenes easily, \\adapting" their visual response to avoid compression or truncation with no apparent loss of detail."

Or Page 3:
"Synthetic and real-world scenes often contain very high contrasts. For example, a scene with dark shadows, visible light sources, caustics or specular reections is likely to contain contrasts as large as 100,000:1 or more."

Or Page 4:
"The ease with which humans view high contrast scenes suggests that models of visual perception may help solve the problem of displaying high contrast images on a limited contrast display. This paper presents two simple methods inspired by the human visual system. In particular, humans form separate but simultaneous judgments of lighting and surface properties as if the scene were perceived in multiple layers [2]. The lighting layer contains most of the high contrasts while most of the image detail and texture is contained in the layers describing surface properties. The rst method, therefore, compresses the lighting layers of an image and leaves the surface properties unchanged. The second method mimics the directional nature of visual adaptation. Because the human visual system adapts preferentially to available light in the direction of gaze, this method adjusts the entire image for best display of a small neighborhood around the viewer's center of attention."

Or here which precedes the quote that you present:
"However, the response of retinal ganglion cells to large local contrasts is bounded by gradual, asymptotic limits. Signals from retinal cells are dificult to measure, but experiments by Sakmann and Creutzfeldt (1969) and others (summarized in [36]) have shown ganglion firing rates in the cat approach a fixed upper limit as local contrasts exceed about 100:1, and their plots of firing rates revealed a family of smooth asymptotic curves. Retinal ganglion cells may directly encode the small contrasts (<100:1) caused by reflectance variations in a viewed scene, but the huge contrasts possible at illumination boundaries must drive both ON-center and OFF-center cells towards their asymptotic limits."

This describes localized limits at a high contrast boundary. Your assertion that the 100:1 limit applies across a scene is completely erroneous and flatly rejected by the very paper you cite.

Or continuing in the paper:
"Adaptation has a strong local character because the human visual system adjusts separately at different locations within a viewed scene or image. These adjustments allow simultaneous sensing of texture and detail in both strongly shadowed and brightly lit regions. As a result, human vision almost never clips" as a camera or display might. For example, trees silhouetted against a brilliant sunset may appear featureless black when photographed or rendered, but a human viewer will see leaf colors, bark textures, and other fine details of the tree if any of them subtends more than a few degrees of the visual field. Local adaptation allows us to recover the appearance of the tree within the scene.
Local adaptation depends strongly, but not entirely, on the image within the viewer's small, central fovea. For example, looking directly at the surface of an incandescent light bulb causes the remainder of the visual field to temporarily appear darker, indicating that the bright image on the fovea depressed perceived intensities everywhere. However, if the bulb is at least 20-30 degrees away from the direction of gaze, hand movements that reveal or block a view of the bulb have little or no effect on the apparent brightness of the rest of the scene."

Or again if it's not clear enough:
"Local adaptation is particularly useful when viewing high contrast scenes because small neighborhoods tend to be much more homogeneous than the entire image. Neighborhoods that include both shadowed and brilliantly lit features will have high contrast, but these regions are usually only a small fraction of the entire image."

Quote:


2. http://www.cse.yorku.ca/~wolfgang/papers/hdrwinmgr.pdf
"Furthermore, there is a limit to how much contrast can be perceived in a very small neighbourhood of the visual field. ... The threshold at which this occurs, the maximum perceived contrast, is reported to be around 150:1 [9]."

And again your intellectual dishonest is staggering. The full quote:
"Furthermore, there is a limit to how much contrast
can be perceived in a very small neighbourhood of the
visual field. That is, when the contrast between
adjacent spots on the retina exceeds a particular
threshold, we will no longer be able to perceive the
relative magnitude of that contrast (roughly speaking,
the spot on one side will appear white and the one on
the other - black). If you separate the spots in space,
you will again be able to see their variations in
brightness. The threshold at which this occurs, the
maximum perceived contrast, is reported to be around
150:1 [9]."

Your attempt to take this quote out of context by removing relevant statements from the paragraph is unbelievable.

Quote:


And yes, this has to do with small angles, because it gets even worse if you leave the foveal area. The black and white patterns you like to cite are irrelevant, because our retina has very limited color vision outside the fovea, because the cones (the color-sensitive photoreceptors) are concentrated there, whereas the rods (luminance detectors) are in the periphery. You simply fail to understand that the HVS has complex spatio-temporal processing that primarily results from adaptive processes within a narrow field of view. The contrast adaptation occurs dynamically as we move the foveal area across limited areas of interest with a huge 3D space. However, within each of these limited areas, the contrast does not exceed 100-300:1. As I said, large, immersive projected images will beenefit from higher CR, but if you look at a small image that is covered by your foveal area, you simply won't be able to resolve more contrast than the numbers the scientific literature gives you. So go ahead and deny, I couldn't care less.

I'm not denying that limitations AT a high contrast boundary are significant. Indeed, I've been saying that the entire time since the very beginning, and you only now are beginning to recognize that these figures are for extremely localized features. Further, color vision is irrelevant here as Darin pointed out. Lastly, we have the ability to fix our gaze at different points across a scene, so an image presented by a display device needs to match our abilities to see large contrasts across a scene or image, not just in the extremely limited narrow angles of adjacent pixel groups.

The key point is that both of the papers you cite DIRECTLY and unambiguously support my point: ANSI CR capabilities significantly beyond 100-300:1 are necessary to match or exceed the capabilities of human vision. Indeed, the figures of 100-300:1 are only applicable to extremely limited viewing angles and would be more appropriate to discuss in terms of display MTF and contrast performance at extremely high frequencies, not at the very low frequency of an ANSI Checkerboard pattern.
post #170 of 505
Quote:
Originally Posted by armadillo View Post

1. http://www.cc.gatech.edu/gvu/animati...s/hicont98.pdf
"The huge input range of the human visual system is largely the result of adaptation processes.
As summarized by Walraven and colleagues [36], several researchers have isolated the response of retinal photoreceptors from adaptation e ects by measuring cell responses to very brief flashes of light. Their measurements indicate that without adjustment by adaptation processes, responses vary only in a narrow range of light intensities covering about two factors of ten, or 100:1".

Correct. You will find references after references with the same conclusion. The limiting factor appears to be the retinal neurons, as explained in this reference I was given:

http://www.pubmedcentral.nih.gov/pic...1&blobtype=pdf
post #171 of 505
Do the test I asked you to do and tell me how many boundaries you are able to discriminate outside of the foveal area. It doesn't matter how much CR you monitor has. What matters is what your fovea can see with 300:1 CR. If the contrasting areas outside of that area, the HVS will be worse. I really do not understand why people are so adamant about issues they obviously do not (or do not want) to comprehend.
post #172 of 505
Quote:


What matters is what your fovea can see with 300:1 CR.

What also matters is that AVS readers aren't stupid. They know we can move our eyes around to view different areas across a scene.

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I really do not understand why people are so adamant about issues they obviously do not (or do not want) to comprehend.

Because it is profoundly important to reject the claim that ANSI CR beyond 300:1 (or whatever similarly low number you want to choose) matches or exceeds the capabilities of human vision. Your attempts to obfuscate the issue just makes this task more difficult because you put forward erroneous claims that misrepresent the actual discussions in the papers you cite. Your willigness to misrepresent (knowlingly or ignorantly) relevant papers is quite frustrating to people who actually are interested in having a reasonably informed discussion.
post #173 of 505
Quote:
Originally Posted by armadillo View Post

Make a quick test. Read this text with your eyes at the closest possible distance. Then try and discern colors and contrasts outside of your foveal area. Can you eveb see the contrast between the browser's window frame and your desktop? Even if you do, how sharp is that?
...
Do the test I asked you to do and tell me how many boundaries you are able to discriminate outside of the foveal area. It doesn't matter how much CR you monitor has.

If I go as close as I can and still read a word, I am aware of black on white (the text) outside of that, but of course can't make it out to know what it says and am still aware of the white to black transition at the border of my monitor that is probably well over 20 degrees off center. So, what is your point with this test? Of course the boundary isn't sharp out there, but if the CR at that point were lowered then I wouldn't even be aware that there was a change out there. That is, a high contrast ratio there was required for me to be aware that there were 2 levels.

The monitor CR definitely matters as far as whether transitions outside the center of vision are visible or not. The higher the CR (the lower the absolute black for a given white level) the more CR there is for levels to get over the Just-Noticable-Difference boundary.

Again, what is your point with this one? Things outside the foveal area do not just blur to the same level. Do you want them too (which is what happens when there isn't enough difference between them)?

--Darin
post #174 of 505
HHF,

Are you going to address that you said you agreed with:

"1. The HSV may only be able to distinguish ~200:1 contrast across an arbitrarily small angle (e.g. adjacent pixels)"

and yet your original statement was:

"The < 300:1 per visual frame is certainly the CW in the HVS community."

Is your position that the limit is per visual frame, or across an arbitrarily small angle (e.g. adjacent pixels)?

--Darin
post #175 of 505
Quote:
Originally Posted by ChrisWiggles View Post

... Your intellectual dishonesty in quoting these papers is staggering.

...And again your intellectual dishonest is staggering...

I see I was correct in my earlier post about your personal attacks on people who have a different opinion than yours.
post #176 of 505
Armadillo,

In your first post, you said this:

Quote:
Originally Posted by armadillo View Post

This is a fun thread to read. As I see it, there seems to be only one person who got it partially right: Raul GS....

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)....

(Emphasis Mine)

Do you still defend that point, or do you concede that 300:1 is not ample and a higher contrast would be noted? Because I don't even think the people who are on your side of the debate believe that. I'm pretty sure HH wasn't making that point, so you may be the last hold out.

It's a simple yes or no question, do you believe a 300:1 contrast is "ample and a higher contrast ratio would not be noticeable"?
post #177 of 505
Chris: I'm baffled. I explicitly said that the real world in 3D has huge contrasts. The point is that these contrasts cannot be visualized withing the human viewing angle at the same time with the same contrast and same acuity. Our acuity, color and contrast perception is localized to a small area of the retina called the fovea. We are also able to dynamically adjust our eyes to a wide range of incident light. But what cannot achieve is that we resolve the full contrast unless we move the region of interest to a particular area. So as we optimize our vision for a subimage of the entire visual field, the periphery is not resolved in acuity, color, and contrast. If you don't believe me, try and resolve color and contrast outside of the text you are currently reading on screen. It just doesn't work.

As I also said, it would be very desirable to have displays match the real world contrast, because we could then inspect that image by moving our fovea to points of interest and adapt the contrast relevant to that area. This would all be within a single frame. But if you want to see the entire image within the fovea at the same time, it cannot be too large and will be limited by the CR your eyes have adjusted to.

As to the text that states you can discern details in a tree against the sunlight, I did that test and I can say that my eyes cannot resolve contrast next to the sun. As soon as I blank out the sun, the tree is clearly visible in high contrast.
post #178 of 505
skogan: As I said in several posts, there is benefit to higher contrast displays if the image is larger than your effective foveal area, i.e., when your eyes are allowed to move about the image. So in the case of TV monitor, CR would not matter. If you sit in front of a projection screen, then it will matter, because your eyes can adapt to "subimages" of the larger picture. So I guess my statement was not accurate. It really depends how you look at the image that is presented to you. If you can see the entire image at once in the foveal area, then it doesn't matter. If you have an immersive HT that extends beyond the fovea, then it will matter. Finally, even in the latter case it will only matter if the scene you are viewing is "slow". So a music video with fast cuts and fast changing contrasts will not benefit from higher contrast, because contrast adaptation takes time. So static scenes or slow pans, where your eyes can move and adjust will see significantly more detail.
post #179 of 505
Quote:
Originally Posted by armadillo View Post

skogan: As I said in several posts, there is benefit to higher contrast displays if the image is larger than your effective foveal area, i.e., when your eyes are allowed to move about the image. So in the case of TV monitor, CR would not matter. If you sit in front of a projection screen, then it will matter, because your eyes can adapt to "subimages" of the larger picture. So I guess my statement was not accurate. It really depends how you look at the image that is presented to you. If you can see the entire image at once in the foveal area, then it doesn't matter. If you have an immersive HT that extends beyond the fovea, then it will matter. Finally, even in the latter case it will only matter if the scene you are viewing is "slow". So a music video with fast cuts and fast changing contrasts will not benefit from higher contrast, because contrast adaptation takes time. So static scenes or slow pans, where your eyes can move and adjust will see significantly more detail.

Okay, well then you can understand why we disagreed with the ISF tech's who were saying that 300:1 was all that we needed for front projectors, and why some people disagreed with you.

I don't know enough about the subject to agree or disagree with your new position, but it sounds reasonable. I guess I don't really care either way. But the old position - the one the ISF tech's are preaching, that's the one that we were saying is demonstrable wrong. And I think we are all in agreement on that point now - we do benefit from projectors with over 300:1 Ansi CR.
post #180 of 505
Quote:
Originally Posted by darinp2 View Post

HHF,

Are you going to address that you said you agreed with:...

Is your position that the limit is per visual frame, or across an arbitrarily small angle (e.g. adjacent pixels)?

I did not know that was an open question.

The HVS can discriminate differences in light intensity of < 200:1 (99.999 % pop),at any given instance in time per visual frame.

A visual frame is defined as your field of view, surrounding a fixation point as in the illusion test I posted above.
http://vision.psych.umn.edu/~gellab/...Paper_Kwon.pdf

The reason I posted that link is that it gives a simple indication of the small CR of a visual frame . The reason one cannot perceive the second image for a few seconds is that the adaptation mechanisms have moved the visual frame's dynamic range window. Literally, the frame's CR window is outside the range of the slightly grey disk so if is compressed into the background! If the CR was as large as 10^5 as has been suggested, no adaptation would have occured, ant the slight grey would not have vanished!

At least that is my misunderstanding of the startup's researcher's explaination of the test.
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