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Problems with Color Management

PostPosted: Sun Nov 15, 2009 7:39 am
by sveto
Hello Axel,

I hope you can help me. I just purchased FPV, and i can't get the Color Management working properly. My OS is Windows 7.

In the options Color Management is on, and as ICC profile i have chosen my monitor profile (made with Quato iColorDisplay). Unfortunately tagged sRGB-JPGs are not shown correctly, dark tones block-up and are oversaturated. CaptureNX shows the pictures correctly, as does the Photoshop CS4 trial.

Have i overlooked something? Could it be a bug in the color management implementation of FPV? I could post a screenshot and/or a photo of the issue, if you think it would help resolve my problem.

Best regards,
Sveto

Re: Problems with Color Management

PostPosted: Sun Nov 15, 2009 2:41 pm
by Axel
Color-management is a hairy topic. Most likely the issue comes from the setup or the image itself. If you did not explicitely set the ICC profile in Windows control panel as your default monitor profile it is possible that only FPV actually uses it. It may also depend on how the image was made and which software embedded the profile (some apps, notably GIMP, fail to properly update the EXIF medatada when converting an image to a different color space, for example if an image was initially shot in Adobe RGB and subsequently converted to sRGB using this software, the EXIF metadata still says "Adobe RGB" on the converted files, and this may affect other apps down the chain).

It may also be a workflow issue, such as "assign profile" vs. "convert to profile" issue. FastPictureViewer uses the Windows Color System underneath, it is very unlikely that you have found a bug in this part of Windows.

Besides that, support issues are handled through the support email, and nothing can be said for sure without submitting the actual ICC profile and an actual image exhibiting the problem.

Re: Problems with Color Management

PostPosted: Sun Nov 15, 2009 5:04 pm
by sveto
OK, fair enough, thanks. I'll send you an email with attachments in the next 30 minutes.
sv

Re: Problems with Color Management

PostPosted: Sun Nov 15, 2009 11:07 pm
by Axel
Just to keep our readers informed... I got the files and I'm looking at them. First thing is that the color transform is performed normally (output a bit dark, but no error), second thing is that this color discrepancy only seems to occurs with this specific (custom) monitor profile.

Re: Problems with Color Management

PostPosted: Mon Nov 16, 2009 2:26 am
by sveto
The problem is that WCS cannot handle LUT-based profiles. Now that i switched to a matrix-based profile, the difference is gone. I have a wee bit of posterizing in the dark tones because of very very slightly darker shadows in the Win7-WCS implementation (that FPV uses), but it's virtually invisible, and Capture NX2 has it too. Photoshops implementation of color management is the best one, but that's to be expected, right? :D

It seems that nobody around has used a LUT-based ICC yet, so no one has noticed a problem. The devil's in the detail...
sv

PS: It's really nice to have quick software support on sunday. 8-)

Re: Problems with Color Management

PostPosted: Tue Dec 01, 2009 8:27 pm
by Axel
Glad to know that the issue was solved.

Nevertheless, to be fair, FPV uses WIC, and WIC uses WCS. Other application (such as PhotoViewer on Win7) seems unaffected so there is no indication that WCS does not support LUT-based profiles, perhaps it's a limitation (or bug) in the intermediate layers. We are looking into this and see if using WCS directly works around the issue.

Update: recent versions of FPV can create WCS color transforms directly.