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Bug #11204

Black crush with activated soft-proof

Added by Björn Sonnenschein about 2 years ago. Updated about 2 years ago.

Status:
Incomplete
Priority:
Low
Assignee:
-
Category:
Darkroom
Target version:
-
Start date:
10/08/2016
Due date:
% Done:

20%

Affected Version:
git master branch
System:
other GNU/Linux
bitness:
64-bit
hardware architecture:
amd64/x86

Description

Hello,
When softproof is activated in the darkroom, blacks are crushed.
My monitor is profiled with an XYZ matrix. Eye of Gnome, Gimp and other applications do not show this behavior.
Could this be related to black point compensation, which cannot be turned on or off by the user in darktable?
If this is the case, I would like to kindly request an option to control black point compensation for soft-proofing.
I have tested this with and without LCMS2 in Adobe RGB and sRGB spaces.

Steps to reproduce:
1. Load an image. It is best to use an image with pronounced dark areas.
2. Enable soft-proofing

with_softproof.png - With softproof (357 KB) Björn Sonnenschein, 10/11/2016 10:24 PM

Without_Softproof.png - Without softproof (451 KB) Björn Sonnenschein, 10/11/2016 10:24 PM

CCXMW-B141PW4 #1 2016-07-14 19-40 sRGB F-S XYZLUT.icc (2.41 MB) Björn Sonnenschein, 10/11/2016 10:37 PM

DSCF6372.RAF.xmp (5.37 KB) Björn Sonnenschein, 10/11/2016 10:50 PM

DSCF6372.RAF (31.9 MB) Björn Sonnenschein, 10/11/2016 10:52 PM

History

#1 Updated by Ulrich Pegelow about 2 years ago

  • Status changed from New to Incomplete
  • % Done changed from 0 to 20

Can you please supply an example (screenshot) so we know what you mean with crushed blacks?

#2 Updated by Björn Sonnenschein about 2 years ago

A pair of screenshots illustrating the issue is attached now.

#3 Updated by Roman Lebedev about 2 years ago

The icc profile in question may be interesting too

#4 Updated by Björn Sonnenschein about 2 years ago

In case that this is caused by the fact that black point compensation cannot be turned off:
I have found a todo note in the source code stating that it is planned to implement a checkbox for blackpoint compensation into the softproof menu. I would like to give it a try and implement it by myself and make a patch, as I consider this a nice starting point to get a bit familiar with DT's source code. Could you please point me to a commit where some similar switch had been added to the GUI to give me some orientation? I could not find one by searching the git logs on my own, sorry.

#5 Updated by Björn Sonnenschein about 2 years ago

ICC profile added. This is the one for my cheap notebook's screen, however the problem does also occur with my Dell UP2516D.

#6 Updated by Ulrich Pegelow about 2 years ago

Yes, you're welcome to work on that. Ideally you should implement it as a pull request in github.

Please also submit your raw image + XMP + ICC softproofprofile to this ticket so we can get a better understanding of the issue.

#7 Updated by Björn Sonnenschein about 2 years ago

Sample raw image with XMP added. As softproof profiles, the built-in Adobe RGB, sRGB and the two linear REC profiles were tested.

#8 Updated by Ulrich Pegelow about 2 years ago

What softproof profile have you been using?

OK, I see. The standard ones.

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