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Bug #8746

Chromatic Aberrations does not remove all distortions

Added by Christian Tellefsen about 6 years ago.

Status:
Triaged
Priority:
Medium
Assignee:
-
Category:
Darkroom
Target version:
-
Start date:
06/04/2012
Due date:
% Done:

20%

Affected Version:
git development version
System:
bitness:
64-bit
hardware architecture:
amd64/x86

Description

The CA module is able to remove most but not all chromatic aberrations. Depending on the particular image or surrounding pixels, distortions may remain in the image.

Notice that while the photographer's jacket is free of distortions, there is still a magenta line along his hood.

To compare I have examples of the same RAW-file processed in Lightroom with and without CA-correction enabled.

From DT, only exposure adjusted: From DT, chromatic aberrations module enabled: From LR, with and without CA corrections: Raw:

Related issues

Related to darktable - Bug #9024: chromatic aberation correction produces artifacts Triaged 10/27/2012

History

#1 Updated by Tobias Ellinghaus almost 6 years ago

  • Affected Version changed from 1.0.4 to git development version
  • % Done changed from 0 to 20
  • Status changed from New to Triaged

Yep, it's misbehaving sometimes. Let's see what we can do about it.

#2 Updated by François Guerraz over 5 years ago

Hi,

DT is usually good at removing CA, but it seems to have a problem with some lenses like those that have apochromatic elements. Which is sort of understandable because they probably have non-standard kind of CA, but which is annoying because we end-up, post-processing, with images with more CA left!

It's particularly conspicuous with a Sigma 300mm F/2.8 APO.

An improvement would be greatly appreciated or at least, would it be possible to have a "manual control"?

I don't know how the automatic CA correction works, but I suppose it has a look at a sample in the corner of the images (where the CA should be more pronounced) to determine what are the CA coefficients. I noticed that images with little contrast in the overall image (like a picture with a lot of snow and sky), DT does a very bad job at correcting the CA.

Cheers.

François.

#3 Updated by Roman Lebedev about 4 years ago

  • Related to Bug #9024: chromatic aberation correction produces artifacts added

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