Quote:
Originally Posted by LBFilmGuy /forum/post/15001506
Interesting observations.
I'll try to crank my picture up some more the next time I watch a BD and see if I notice anything major.
Always worth evaluating different points of view. I am still on the fence as to the "clipping over 235" in the digital realm issue.
Even Chris Wiggles threw his opinion in...
http://www.avsforum.com/avs-vb/showt...3#post15004483
QUOTE - "It is not surprising then, that in well mastered content, excursion beyond 235 is minimal, but it still remains for peak white features, and is visibly degraded when that detail gets clipped off in the playback chain. Less stringent terminology describing 235 might leave many mastering houses trying to push nominal whites well above that all the way close to 254 in a "brightness" war kind of like the loudness wars in audio which we all despise. But read fully and understood more completely, it is very explicit that occassional excursion beyond nominal white 235 is not only allowed, but expected, and that headroom is explicitly designed into video standards to maintain the integrity and quality of the content. Ideally, we'd all be watching on reference CRTs, which don't clip, and on playback systems that don't clip, but for many reasons CRTs have fallen out of favor for home viewing since the viewing environment and needs are often significantly different.
The question of where to set a digital display's clip point is unique, again because in the studio on a CRT this problem is not confronted because the CRT doesn't clip, doesn't have the hard white point like a digital, and everything to 254 is preserved and displayed on the CRT.
So when confronted with a different white-point behavior on a digital display, you have to make a tradeoff between preserving small amounts of peak white details, versus higher contrast ratio (which is often a limitation on digital displays). How you reach this compromise depends on how important peak white detail preservation is to you (for many it is minimal), versus slightly increased CR performance.
But it is important to understand that when you have a digital video source, usually it is not as if 235 is a hard peak white point, there will be values above that, even if there aren't very many. Is this a big deal? I guess it depends on your perspective. But stating that one should simply align their digital display's peak white point to 235 and hard clip or being to colorshift detail above that (even if rare) is oversimplified and somewhat misleading. However, that may be a reasonable setting one might arrive at, I just hope they arrive at that setting understanding the compromise they necessarily are making on their digital display, just as someone aligning to 254 should understand that particular compromise. Or anything in between.
And as I've said before in many previous threads, I don't advocate one particular choice for digital users since I use a professional CRT, and I don't encounter this compromise in my own viewing. When I calibrate digital displays, I generally leave a few clicks above 235. But since I don't live with these settings on my own system, I don't offer this as a prescriptive suggestion, since that would vary on the display I was using. But since I'm viewing on a CRT, and nothing clips, I don't really face this problem." -
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My personal question then in that thread is, since you can go either way with this arguement, this...
QUOTE - The second compromise to lowering contrast appears to be the negative effect on how a 235 reference white is handled by your display as a result and the accuracy of the white you see versus the white on the disk.
EXAMPLE...
At the time of mastering, a DVD is encoded with a reference white pixel in a given scene to be sent up the chain to the display as a level 235 reference white on the digital video levels scale (16-235). At the end of the day, it should be a reference white pixel when it arrives and when it is displayed. This is how my brain sees it. This is a truth. Right?
Now if the user has lowered the overall contrast of their digital display to expose whites above 235 on the scale, they have not actually created brighter pixels in the above white zone. They actually have in fact lowered the intensity of the original level 235 in order to see or "notice" white levels above it. It (235 white) had to become dimmer so that the 5% above white (243?) would show next to it or be "apparent" to your eye. The truth then is that it no longer is a 235 White pixel on the screen. you've knocked it down. It's now more like 227 or whatever. The only pixel on the screen now that is the intensity of a 235 reference white is the 5% above white signaled pixel. Mathematically, there is no other way to look at this as far as I can see knowing digital the way I do.
So is this not an error? A de-calibation? The Reference White Point on your display is now in an uncalibrated state? What I see and what the telecine operator expected me to see are now 2 different things. Is that not exactly what will happen?
That to me logically, is the other compromise to lowering contrast to expose above white. You unintentionally knock white out of calibration versus the content on the disk. -
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That said, there are DEFINATELY situations when anything over 70 is overpowering expecially to the eyes and that is when I am on my TV analogue connections. The set handles Contrast like Brightness. When over HDMI from my BD30 it is not like that. Contrast only seems to change the white bar representation. I said that before I think. Sorry.
I am checking with some friends for a light meter. I want to see technically if 60 to 90 (talking HDMI sources only here) contrast has any extra light output that can be measured from an all white screen. My eyes say no. But they can be wrong. But if a light meter confirms that there is no real difference? then really there is no "eye strain" arguement either. It might just be a calibrators preference dependant on which theory to side with. Kill 235 to force a digital to behave kind of like a CRT for a few extra highlights in the whites? Or leave 235 in tact the way the disk is encoded and actually keep the Contrast where the ratio is maximized and you get the contrast ratio the mfg sold you. Every penny's worth! Or somewhere in between.
C.