Chroma resolution v peak white - AVS Forum
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post #1 of 14 Old 01-18-2013, 12:49 PM - Thread Starter
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My setup is a LG 55LW550T fed by PS3.

Everywhere states that the PS3 should be set to YCbCr with super-white on so the display gets below black and above white signals, however using the spears and munsil disc my display fails the chroma multiburst test on the thinnest vertical lines. If I change the ps3 to output rgb then the display passes the test.

My question is: is it better to have full chroma resolution and lose above white or keep above white and lose chroma resolution?
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post #2 of 14 Old 01-19-2013, 03:21 PM - Thread Starter
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Anyone have an opinion on this?
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post #3 of 14 Old 01-20-2013, 03:10 PM
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Other than test discs, there should be no content on Blu-ray with above-white information. Use RGB.
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post #4 of 14 Old 01-20-2013, 03:16 PM - Thread Starter
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Thanks.
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post #5 of 14 Old 01-20-2013, 05:47 PM
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That's not correct. In fact, all or nearly all Blu-ray discs have above white content. It is present in specular highlights... reflections off of water, chrome, crystal chandeliers, etc. Fortunately none of the above white data has anything to do with image detail and it's damn near impossible to detect it by eye (you need a software app that highlights all the above 235 luminance pixels in some obnoxious color so they become obvious... which has been done quite few times, possibly even here on AVS).

Since there's no image detail in the pixels above 235, you MIGHT (but probably won't) notice anything in images if the display is not showing above white. On the other hand, you probably won't notice the difference in the test pattern between YCbCr and RGB either. So pick your poison.
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post #6 of 14 Old 01-20-2013, 11:33 PM - Thread Starter
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As much as I thought. I do notice a difference in test patterns between YCbCr and RGB only on the chroma multiburst and zone plate patterns. I'm not sure how this translates the real world material though but I'm going to calibrate to RGB
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post #7 of 14 Old 01-21-2013, 07:00 AM
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Quote:
Originally Posted by Doug Blackburn View Post

That's not correct. In fact, all or nearly all Blu-ray discs have above white content. It is present in specular highlights... reflections off of water, chrome, crystal chandeliers, etc. Fortunately none of the above white data has anything to do with image detail and it's damn near impossible to detect it by eye (you need a software app that highlights all the above 235 luminance pixels in some obnoxious color so they become obvious... which has been done quite few times, possibly even here on AVS).

Since there's no image detail in the pixels above 235, you MIGHT (but probably won't) notice anything in images if the display is not showing above white. On the other hand, you probably won't notice the difference in the test pattern between YCbCr and RGB either. So pick your poison.

what about the issue where converting YCbCr into RGB results in values greater than 245 in one or more of the color channels? is that content also not true image detail? just curious, since Sotti has posted the following several times in many threads (the following links are from one of the more recent threads)

http://www.avsforum.com/t/1445560/video-games-should-i-bother-adjusting-in-game-brightness-options#post_22720257

http://www.avsforum.com/t/1445560/video-games-should-i-bother-adjusting-in-game-brightness-options#post_22723237

http://www.avsforum.com/t/1445560/video-games-should-i-bother-adjusting-in-game-brightness-options#post_22727446
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post #8 of 14 Old 01-21-2013, 08:45 AM
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Quote:
Originally Posted by Chronoptimist View Post

Other than test discs, there should be no content on Blu-ray with above-white information. Use RGB.

Quote:
Originally Posted by Doug Blackburn View Post

(you need a software app that highlights all the above 235 luminance pixels in some obnoxious color so they become obvious... which has been done quite few times, possibly even here on AVS).

It has been posted here on AVS.. Stacy Spears posted these frame caps a few years ago - "Hot pink means one of the three RGB channels contains a value above 235. Green means one of the three RGB channels contains a value below 16."





Mr.D also posted:
Quote:
I say on a professionally mastered BD the vast majority of all pixels with values above 235 are scaling artifacts (ringing in other words).

I've checked this , others have checked this. We posted the information on here.

I've looked at work that I did myself and compared it with the BD version and I am 99.9% convinced ( tolerances being what they are) that targeting a white point around 240 is the absolutely best way to set peak white on a video display.

~

Now material on BD is carefully color corrected with the leisure of time. Live broadcast material doesn't have this luxury so potentially on occasion can excurse a little more often and has a tiny bit or real picture info . However its usually so blown anyway in this range that losing the pixels outside 240 has not visible effect on the image.

I've not found any of the more esoteric issues with hard clipping at 240 that other people have hypothesized .

Its 240 for me these days and it looks noticably better than taking up dynamic range with junk.

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post #9 of 14 Old 01-21-2013, 10:44 AM
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Cb and Cr have a digital range of 16-240. Only the Luminance coordinate is supposed to produce 100% white at 235. So "above 235" data is already present in YCbCr also.

RGB is a perceptually awkward color space to work with and things you might not expect can happen in conversions - that's just the way it is.

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post #10 of 14 Old 01-22-2013, 07:41 PM
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Quote:
Originally Posted by Doug Blackburn View Post

Cb and Cr have a digital range of 16-240. Only the Luminance coordinate is supposed to produce 100% white at 235. So "above 235" data is already present in YCbCr also.

RGB is a perceptually awkward color space to work with and things you might not expect can happen in conversions - that's just the way it is.

So, is there any real point to calibrating to 255?

As opposed to maximizing dynamic range from 16-235?


On my Samsung LED-LCD, I can set backlight 25% (the equivalent of a 15 fL difference) lower if I calibrate to 235 vs. 255. I can't really calibrate to a point in between 235 and 255 like 240 since green and blue never clip even at 109%, only red does. This is why I leave off Super-White on the PS3 when calibrating to 235 (since it makes the white clipping pattern look neutral white instead of very pink).
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post #11 of 14 Old 01-22-2013, 08:03 PM
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All of the examples posted are either compressor artifacts (the majority) specular highlights (not detail) over-exposed areas (again, not detail) or all three. In fact they back up exactly my point, which is that there should be no picture information outside of the 16-235 range.

Nothing should be hitting 100% saturation and exceeding 235 RGB.

Most of the examples given seem to be broadcast and not film, and the Dark City example looks very different from my Blu-ray (much more saturated) so either there are multiple encodes, it has not been decoded correctly (e.g. with DXVA there might be some kind of post-processing) or that's an HDTV rip. Same thing for Signs - that should not be a 16:9 image, it looks like an open-matte broadcast.

signs0gqfr.png

And when you do a full color analysis rather than simply coloring everything above white pink, it tells a different story:
signs-levelsq0qkx.png

Also: note the big spike at 16 and at 235 - that's the range they are encoded for. Values outside of that are compressor artifacts/noise.

Are you really seeing a big difference between 16-235 and 16-240, other than 16-240 having non-white highlights?
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post #12 of 14 Old 01-22-2013, 09:17 PM
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If I understand correctly, a setting beyond standard 16-235 introduces or enhances artifacts in the image. When calibrating my JVC RS-55 projector using the AVS disk through an OPPO BD-93, I was not able to eliminate image moiré. I will see what effect changing the HDMI setting to standard.

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post #13 of 14 Old 01-23-2013, 11:13 AM
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Quote:
Originally Posted by PlasmaPZ80U View Post

So, is there any real point to calibrating to 255?

As opposed to maximizing dynamic range from 16-235?


On my Samsung LED-LCD, I can set backlight 25% (the equivalent of a 15 fL difference) lower if I calibrate to 235 vs. 255. I can't really calibrate to a point in between 235 and 255 like 240 since green and blue never clip even at 109%, only red does. This is why I leave off Super-White on the PS3 when calibrating to 235 (since it makes the white clipping pattern look neutral white instead of very pink).

Well, if you are setting up the TV to show any information above 100% white (you won't see values in actual content higher than 254, as that's a hard cut-off point used by those creating the content for discs and 254 is roughly 109% white), you don't want to see pastel colors in the specular highlights like you might if 101%-109% is not relatively color accurate. So you want to look at what's going on above 100% if the TV is going to display content above 100% just to avoid unexpected off-color issues.

On the other hand, I've never known anybody (including me) who can tell if what they are looking at is setup for 0-100% or 0-109% without test patterns and possibly without a meter. Just looking at the content doesn't provide enough information to be able to tell if you are seeing 100% or 109% as the peak white level.

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post #14 of 14 Old 01-23-2013, 07:11 PM
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Quote:
Originally Posted by Doug Blackburn View Post

Well, if you are setting up the TV to show any information above 100% white (you won't see values in actual content higher than 254, as that's a hard cut-off point used by those creating the content for discs and 254 is roughly 109% white), you don't want to see pastel colors in the specular highlights like you might if 101%-109% is not relatively color accurate. So you want to look at what's going on above 100% if the TV is going to display content above 100% just to avoid unexpected off-color issues.

On the other hand, I've never known anybody (including me) who can tell if what they are looking at is setup for 0-100% or 0-109% without test patterns and possibly without a meter. Just looking at the content doesn't provide enough information to be able to tell if you are seeing 100% or 109% as the peak white level.

interesting... my PS3 can clip WTW simply by turning YCbCr Super-White OFF or using RGB, so BD and DVD playback is fine with my TV calibrated for accurate grayscale/RGB tracking up to 235

however, other devices like the Xbox 360 (and possibly my Comcast HD STB) just pass WTW all the time no matter what color space or level settings are used... a Samsung BD player that came with my TV but I don't use also shows WTW all the time (with no way to clip it at the player like on the PS3)
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