Does anyone actually believe the nonsensical contrast ratios specs? - Page 7 - AVS Forum
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post #181 of 185 Old 02-25-2014, 08:42 PM - Thread Starter
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Originally Posted by stanger89 View Post

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Originally Posted by trans_lux View Post

That being said it was clear to me that the Sony had superior contrast.

Well there ya go, this is exactly what most of us have been arguing. On/Off contrast is important, visible, and applicable to real world situations (regardless of whatever the situation is with manufacturers' specs), this is exactly what you saw with the DPI vs the Sony, the DPI undoubtedly had superior ANSI contrast, but the Sony's superior On/Off contrast was visible.

I never said that a projector like the Sony or the JVC didn't have excellent black levels.
I just question the really high CR numbers, how they were derived and did they have any practical applications.
Even if these ratings were true can we even perceive these suggested differences?
The common thought is we can see roughly up to 1,000,000:1 but only in extreme darkness for an extended period of time around 30min, with no light stimulus-think can't see my hand in front of my face. In normal day to day conditions we see somewhere around a max of 1000:1. It takes very little light to greatly reduce our ability to distinguish contrast. Also as contrast goes up our abilities to determine difference diminish greatly.
Our contrast sensitivity is non-linear. Our eyes are relatively less sensitive in the dark areas of an image than it is in the bright areas of an image. This variation in sensitivity makes it much easier to see small relative changes in the bright areas of the image than in the dark areas of the image.
Sadly our contrast perception peaks around our early 20's and declines from there.
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post #182 of 185 Old 02-25-2014, 09:26 PM
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Originally Posted by trans_lux View Post

I never said that a projector like the Sony or the JVC didn't have excellent black levels.
I just question the really high CR numbers, how they were derived and did they have any practical applications.
Even if these ratings were true can we even perceive these suggested differences?
The common thought is we can see roughly up to 1,000,000:1 but only in extreme darkness for an extended period of time around 30min, with no light stimulus-think can't see my hand in front of my face. In normal day to day conditions we see somewhere around a max of 1000:1. It takes very little light to greatly reduce our ability to distinguish contrast. Also as contrast goes up our abilities to determine difference diminish greatly.
Our contrast sensitivity is non-linear. Our eyes are relatively less sensitive in the dark areas of an image than it is in the bright areas of an image. This variation in sensitivity makes it much easier to see small relative changes in the bright areas of the image than in the dark areas of the image.
Sadly our contrast perception peaks around our early 20's and declines from there.

I'm not sure where people keep coming up with this stuff. I wonder if anybody ever does their own checking to see if it matches what they think something meant. I think much of the stuff out there by people who are supposed to be experts is really from people who are ignorant. That one wasn't pointed at you TL, but I already mentioned the contrast sensitivity test once. It is a reciprocal function. Do you know what that is? They take the contrast ratio and basically flip it to give a score, so 100 is not even in the same ballpark as 100:1 contrast ratio we talk about around here. It is more like 1.01:1, or a 1% difference.

And since it is a reciprocal the fact that our contrast sensitivity goes down means that we need more contrast ratio in order to be able to see detail. That fact would be missed by some writer's out there who didn't seem to comprehend that the contrast sensitivity test measured the least CR our person could see, not the most.

I'm thinking maybe we should make a rule that those who believe the total range of image CR that a person could see across even given lots of time is 1,000,000:1 shouldn't be allowed to drive at night. They would likely be a danger if that were truly the case.

Here is a link to some data from NASA:

http://msis.jsc.nasa.gov/sections/section04.htm

If people look for moonlight in there they can see the table where white paper in sunlight is about 10^4 and white paper in moonlight is about 10^-2. That is a range of 1,000,000:1. Is there anybody here who thinks those are the limits of human vision given time and that humans either can't even see down to white paper in starlight (about 10^-4) or above white paper in sunlight. How would a person be able to see the glint off the chrome on a white car at the same time as the car if their upper limit was white paper in sunlight?

I've tested myself and could see detail on both ends outside a range of about 2 million to 1 in less than 3 minutes. That is the light levels I was looking at, not the light levels at the back of my eye (since the light levels of the things being looked at is what we are talking about for image CR range and if anybody thinks it is the range at the back of the eye or in the brain they are confused about what is relevant for total image range needed to hit the limits of human perception).

I recall one ignorant reviewer from Australia IIRC who each year would get a projector and proclaim that the blacks looked better than last year, but now they had reached the limits of human perception. I wondered if he would ever catch on that he didn't comprehend the subject matter or he wouldn't have proclaimed something that wasn't true the year before and that seeing beyond what he had claimed was possible before should have given him a clue that he didn't really know what was possible.

--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 #183 of 185 Old 02-26-2014, 07:21 AM - Thread Starter
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Darin thanks for the info.
There is a lot of contradictory information on human vision capabilities especially when it comes to contrast ratio perception.
Just do a google search.
One aspect that I see is a constant is that our ability to perceive contrast degrades as we age. frown.gif
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post #184 of 185 Old 02-26-2014, 07:33 AM
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I think trans_lux use of 1,000:1 contrast at any point in time and 1,000,000:1 human vision adaptation overtime  30 minutes, was just using guesstimates to illustrate a point. That trans_lux believes that projectors claiming contrast in the hundreds of thousands to one are claim contrast so high the viewer would need time for their eyes to adapt to see both ends of the range.

 

A quick Google on the subject seems to indicate that human vision is generally said to be about 10,000:1 contrast any point in time and 10,000,000,000:1 human vision adaptation over time photopic (> 3 cd/m2) to mesoptic (<3 cd/m2 >0.003 cd/m2)  to scotopic (< 0.003 cd/m2). Fast transient adaptation say coming out of a dark tunnel into light or going from a bright daylight to a dark cave takes seconds to shift sensitivity from one vision range to another during which the person maybe temporally unable to see much. Slow adaptation takes about 5-7 minutes for the switch in sensitivity dominance between photopic and scotopic. Full adaptation from photopic to maximum sensitivity of scoptic vision takes up to 45 minutes.

 

It seems to me human vision maybe photoptic range of about 10,000:1 with no adaptation time, mesoptic about 1,00:1, scotopic about 10,00:1, giving a combined total of about 10,000,000,000:1 contrast range with adaptation time as the viewer shifts between photoptic - mesoptic - scotopic. 

 

As to projectors with contrast of a hundred thousand or higher.

Would the viewer need time to adapt to see both ends of the contrast range? 

If they do how much time would they need to adapt?

Is there or with ever increasing contrast will there be a down side? If the projected image is the only source of light, it is a perfect otherwise pitch black no reflective room, how high a contrast range will cause temporary inability to see what is going on or temporary viewer discomfort if there are raid change in brightness or eye strain in dark scenes or glare in bright scenes?

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post #185 of 185 Old 02-26-2014, 07:49 AM - Thread Starter
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I do know that when I run two lamps-about 57ftl-for group viewing of sporting events very bright scenes namely commercials with effectively full white fields are not only blinding but it takes many minutes to adjust after the game is resumed.
The real question is that given that we're now able to achieve significantly brighter images do scenes with high contrast continually reset our ability ability to perceive contrast? I know our eyes are dynamic but the general consensus is that even low light stimuli greatly effects our ability to see contrast.
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