Dumb question. but the list is so quiet. I have a GeForce 1070 video card in my Win10 PC. In Photoshop 2019, under Preferences > Performance, I find GPU options. And under those options, there is a "30 bits display" option. Is that what I think it is? I don't dare activate it in case I blow my machine up. But, really, 10 bits per channel display? Instead of the traditional 8 bits? I suppose Photoshop would never display such an option *if* the video card did not support this. Best / Roger Breton www.graxx.ca
Yes some displays can differentiate 1024 steps in a single channel zero to one gradient. What I mean is, if you draw a gradient from pure red (1.0 0.0 0.0 1.0) to black (0.0 0.0 0.0 1.0) on an 8 bit display with an 8 bit pipeline (app, operating system, graphics card, the whole nine yards), not taking into account irregularities in either the source or destination profiles, you’d see 256 steps if you were to zoom in closely. Each stage of the pipeline only carries 8 bits of information, so you’d never see more than 8 bits worth of differentiation, 256 steps. This is easier to prove to yourself in a narrow range gradient across a visibly large section of the display, so let’s say you draw a gradient from 64.0/255.0 to 67.0/255.0 in the red channel across 128 pixels. You’d see four bands each about 32 pixels across. On a 10 bit display if the app, operating system and graphics card all support 10 bit, you’d see four times that many steps, so 16 steps between 64 and 67, or 1024 steps between 0 and 255.
Indeed, there are plenty of areas that all need to be supporting a high bit video path as you outline. Here's a test file that makes it easy to see in Photoshop, at 100% view, if the path is high bit or not. One should see no banding. http://digitaldog.net/files/10-bit-test-ramp.zip Also, on the Mac, it's possible to see this reported in System Report>Graphics/Display but I have no idea if there's an equivalent on Windows. Andrew Rodney http://www.digitaldog.net/
On Feb 20, 2019, at 12:28 PM, John Gnaegy <gnaegy@apple.com> wrote:
Yes some displays can differentiate 1024 steps in a single channel zero to one gradient.
What I mean is, if you draw a gradient from pure red (1.0 0.0 0.0 1.0) to black (0.0 0.0 0.0 1.0) on an 8 bit display with an 8 bit pipeline (app, operating system, graphics card, the whole nine yards), not taking into account irregularities in either the source or destination profiles, you’d see 256 steps if you were to zoom in closely. Each stage of the pipeline only carries 8 bits of information, so you’d never see more than 8 bits worth of differentiation, 256 steps.
This is easier to prove to yourself in a narrow range gradient across a visibly large section of the display, so let’s say you draw a gradient from 64.0/255.0 to 67.0/255.0 in the red channel across 128 pixels. You’d see four bands each about 32 pixels across.
On a 10 bit display if the app, operating system and graphics card all support 10 bit, you’d see four times that many steps, so 16 steps between 64 and 67, or 1024 steps between 0 and 255.
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Also worth pointing out that all of the stages in the display pipeline need to carry 10 bits of information, app, graphics card, operating system, display, source space and any filters applied, and probably other things I’m not thinking of. If any of those only carry 8 bits of info, you’ll only see 8 bits of differentiation. You’d want to try the gradient experiment in at least a 10 bit space, not sure if Photoshop has a 10 bit space but you can specify 16 bit as the source space.
participants (3)
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Andrew Rodney
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graxx＠videotron.ca
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John Gnaegy