Originally Posted by jong1
Andy, I'm not sure we can read anything into your desktop images, since your camera could be exposing things slightly differently between shots. I think we need calibrated images as in my zip above, to be sure what is happening. I think then you may see you get the same video AND desktop levels between RGB limited and RGB full.
Although there can be very
slight differences of exposure due to the lens' automatic aperture, the differences are unnoticeable unless you're doing something like stop-motion animation (the reason why for instance, Corpse Bride was done with Nikon manual aperture lenses on a Canon digital SLR). The exposure differences are nowhere near to account for the difference/compensation of 0->16 values. Just eyeballing it, I figure the difference required would be higher than 1/3 stop which is the minimum exposure step in most digital cameras. Even by the lowliest camera standard, it would be useless if it couldn't resolve such a difference with its aperture timing.
Besides that, all of the pics that are expected to look the same given the settings, look the same (like 1.1.3
). The ones that are expected to be compressed (1.2.3
) or clipped (2.1.3
) also show it. The likelihood of the desktop levels really being off but by random exposure differences somehow compensating to show as expected, in all of those individual cases, is very slim to say the least.
Exposure differences, more importantly, cannot compensate for compression/expansion, only for overall brightness of the whole range.
I just used regular pics to be compared to each other, cause there are only 3 scenarios possible, correct, clipped, or compressed. I can see all three in some examples above just as expected, so I just used pics with detailed dark areas. They are not meant to be compared to the video pictures, I just wanted to know that the desktop was being changed at all.
This is what I am seeing here:
- RGB Full and Limited seem to output the same desktop levels. The driver (10.2) just seems broken. They both output what should be RGB Limited, i.e. the desktop is compressed so RGB "0" becomes RGB "16".
What type of input are you setting your display to? If you set the input of your display to 0-255 input, do both pixel format limited and full in CCC look the same?
- Using Full DR in combination with RGB (effectively limited regardless of setting) causes black crush. BTB is lost and video black becomes luma "0"
I think this could be due to your display not accepting full 0-255 signals, but that wouldn't be a problem with the card.
- Using Limited DR with RGB (Limited) outputs consistent levels with desktop. Video black is luma "16" and BTB is restored.
So it seems that when RGB is used video (HD DXVA video?) is always expanded. However, by using the "Limited DR" option this effect can be reversed by first compressing it, before it is subsequently expanded.
I came to this a bit late and have not digested what all of you have been saying. I've only really digested Andy's info! But it seems to me that only YCbCr works as it should (with DR set to full). I can also get consistent levels for desktop and video (but maybe only HD, I have not tested SD) by setting "Limited" RGB and "Limited" DR, but this seems like two errors cancelling each other out to me. It looks like, when RGB is set, video (HD? DXVA?) is always treated as though Full RGB is selected, but RGB in fact is always working in "Limited" mode!!
Desktop aside, Andy, I think all of this is consistent with what you are seeing if your display clips <16, as it seems to.
It only clips when input is set to 16-235 or YUV though. With 0-255 input (section 1 in my post) it's not clipping anything. It seems to me that your and Somy's observations are consistent with your displays not taking in 0-255 properly?