Adobe: Just a reminder, this color-management problem that I reported against Photoshop CS5 is still around:
It's illustrated here in this screen grab, showing the visibly inaccurate result of Photoshop's transform, done in the GPU, from RGB values in the ProPhoto RGB color space to the sRGB IEC61966-2.1 color space. Note the circular banding and color shifts in what should be a perfect gray gradient.
Do you think you could find it in your hearts to fix this before moving on to layer more features on an imperfect code base?
Noel; by chance I think I have hit the same problem, and it has been driving me crazy. Working on a series of images for an upcoming show and I am seeing the same color artifacts in areas of grey just above black. This destroys the image completely and mucks up the print. My current workaround is to convert the grey scale then convert back to RGB and the banding and color shift goes away. But this approach does not give an optimum print when using the Advanced Black & White for my Epson Printers, The only way I can get an exhibition quality print is to use Quadtone RIP.
So yes, pretty please please fix this problem - by the way never noticed this in CS5
As I've only seen the issue with transforms done by the GPU-resident color-management code, which as far as I know is only used for displaying images on the monitor, I'm curious how it could manifest in the document, ultimately making it into a print.
I don't doubt that you're seeing something wrong, but I wonder if it could be different issue (or related in some way I'm not seeing)... Can you go into a bit more detail how you arrived at a case where color inaccuracy was immortalized in the pixels in a document? That would turn this problem from a display annoyance into a serious image quality bug in my opinion.
I might have jumped the gun here - what got me excited was seeing the same color banding in my shadows. But further testing shows some weird stuff that I have not figured out yet.
Scanning a B&W negative as an RGB TIFF I see this same colored banding in the shadows. What makes it weird is going to the channel mixer and clicking Monochrome and the colored banding is still there and prints as such. Might be a video driver problem. But converting to grey scale fixes the issue - go figure.
As I mentioned converting back to RGB fixes the issue and allows me to use my favorite plugin (Silver Efex Pro) to smarten up the image and prints without any banding
Lundberg, perhaps you were looking for the artifacts to reach out and hit you over the head. This is subtle.
If you can't see the artifacts in the PNG I posted above than your monitor/system are not delivering a good quality experience. Try loading it into Photoshop and enhancing it. Then they'll jump out at you.
Not sure I understood that, Mike. Downgrade to what?
I have a video card that's not cutting edge any more - a Radeon HD 5670. If I knew that the new 7850 didn't classify as one of the "certain brands and models of GPU" mentioned by Chris, I'd get one ordered, as it offers about 3x the performance I now have (not that I wait on very much as it is).
In any case, there's a reasonably decent workaround to this issue that results in a net loss of almost nothing - use the Basic GPU mode. And this issue doesn't affect me much as I only rarely work on ProPhoto RGB imagery. But I didn't want it to be forgotten about, as I know a lot of people do use that color space.
Well a good rule of thumb, is let the other guy suffer until you know what you are dealing with.
I have multiple systems and versions running so if things are broken, you can always go to your 2nd choice. Or even 3rd.
Banding always seems to challenge Adobe. Sometimes it works, and sometimes it morphs into some other mess somewhere else. It's a huge job tracking issue, and I see no end in sight for the company.
So, I guess you will need to keep every computer and every version of software available to do your job. Sounds about right for a production environment.
Actually, I'm able to do most everything requiring alternate environments with a small number of Workstations and one Server, in that I create VMware virtual machines for the purposes of generating alternate testing environments. Without virtualization for everything other than testing specific GPUs, I'd have had to fund and build an extensive test lab.
I would like to include myself in the list to request the Adobe Photoshop CS6 team to look into the discolorization issue. I am using the entry level nVIDIA GT 430 for its basic openCL features for PhaseONE CaptureONE PRO.
I created a 16-Bit monochromatic image in CaptureONEPRO 7 and opened in CS6. My RGB working profile is ProPhoto and my 16-BIT BW TIFF is in the ProPhotoRGB space. With the GPU settings to "Normal" and "Advanced," I could see the discolorization and banding on my images. I have found that if I go to "View" and click on "Gamut Warning," the discolorizatioin seem to disaappear.
Having the GPU to "Basis" clears everything up as Noel Carboni first reported. I only have the banding and discolored appearing when GPU is on "Normal" or "Advanced."