-
1. Re: Strange sRGB soft-proofing behavior
twenty_one Mar 18, 2014 12:22 AM (in response to tozzy)You're right, this doesn't make sense. I suspect there is a bug hidden somewhere in all this, because similar erratic behavior has been reported in other cases. The preview thing I've seen myself.
It doesn't have to be the Photoshop code. Since this affects display, it could be video driver / OpenGL. I haven't checked if this still happens with Open GL basic or off (where display color management is shifted back from the GPU to the CPU).
-
2. Re: Strange sRGB soft-proofing behavior
tozzy Mar 18, 2014 3:08 AM (in response to twenty_one)Yes you're right. I had my suspicions that had something to do with OpenGL. I turned the preference setting back to Basic and the "problem" went away. i think this needs to be fixed... it's very confusing behavior and leads you to wonder if there are other times when the on-screen CMS rendering behavior can't be trusted. Is it a bug in Photoshop, OpenGL, or the video drivers though? I think we need to let Adobe figure that out. How to report this as a bug?
-
3. Re: Strange sRGB soft-proofing behavior
Noel Carboni Mar 18, 2014 5:33 AM (in response to tozzy)tozzy wrote:
it's very confusing behavior and leads you to wonder if there are other times when the on-screen CMS rendering behavior can't be trusted.In my observation there are two forms of color-management implementation, both controlled by Adobe: The first is the traditional Adobe Color Engine as executed by the CPU - this is run if you have the [ ] Enable Graphics Processor setting unchecked or have it checked but are using Basic drawing mode in the Advanced Settings section. Phtotoshop also reverts to this CPU-resident color-management while you are moving a window and when you're using View - Gamut Warning.
The second form is executed by the GPU and is used when in Normal and Advanced drawing modes. This GPU implementation is presumably faster, but is also observably inaccurate under certain specific conditions. For example, if your document is in the ProPhoto RGB color space, it will show subtle color banding in a pure gray gradient.
The GPU-resident color management transforms have also been seen to add multi-value output level jumps, resulting in visible banding, in high bit depth gray gradients, where the CPU-resident code does not.
I reported these inaccuracies to Adobe some time ago, but either the GPU-resident color-management code is inscrutable or they just have other priorities, because the inaccuracies remain.
I just brought all this up, tozzy, since you mention the problem going away when the CPU-resident color-management code is invoked. To retain GPU acceleration for other things, but use CPU color-management, try using Basic drawing mode if you're concerned about getting the most accurate displays from color-management. Remember that you have to close and restart Photoshop after making changes in these settings.
-Noel
-
4. Re: Strange sRGB soft-proofing behavior
tozzy Mar 18, 2014 6:14 PM (in response to Noel Carboni)Thanks Noel - yes as per my previous post, dropping back to Basic fixed the problem. I'm going to leave it on that. I've got enough grunt in the cpu that I don't think I'm going to notice too much of a performance difference. toz


