Image artefacts as a result of vignetting correction

[Jan Wolter]

Hello,

I'm using lensfun (I tested the version 2.8 from sourceforge and the
newest git version 2.9) with digikam (tested with version 4.0 and 4.1)
under Linux Mint 17, 64 bit, Cinnamon. I shoot photos with my two Micro
Four Thirds cameras Panasonic GF-3 and Olympus OM-D E-M1 and I use the
following lenses: Lumix 14mm, F2.5; Olympus 12-40mm, F2.8; Olympus 45mm,
F1.8 and Olympus 17mm, F1.8.

When I apply the lensfun corrections in my RAW development workflow I
get crazy image artefacts in the upper three quarters of the image.
Please compare the screenshots you can find here:
https://www.dropbox.com/s/yk0bkeyqyyo62jw/lensfunProblem-downscaled.png
https://www.dropbox.com/s/hv15up0yurcxxlb/lensfunProblem-crop-100perc.png
The artefacts comes from the vignetting correction (if the subject
distance is >0), because when I deactivate vignetting from the list of
corrections, such artefacts are not present.

The problem occurs with all combinations of cameras and lenses, as long
as for a particular lens vignetting corrections are defined in the
corresponding xml-file under /usr/local/share/lensfun.

Does anyone has the same problem? Or can reproduce it with my raw file,
which you can download here:
https://www.dropbox.com/s/oa717wk8w7vkgmy/P7057624.ORF

Yesterday, I wrote this message to the lensfun mailing-list, because I
suspected that its a problem from the lensfun library. But Torsten
Bronger (I guess he's one the lensfun developers) replies that he can
not reproduce the error with darktable and assumed that it's a digikam
problem: http://sourceforge.net/p/lensfun/mailman/message/32569578/

Can please someone test the vignetting correction with my raw file and
give me feedback?

Best regards,
Jan

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  Jan Wolter, M.Sc.        | e-mail: [hidden email]
  Universitaet Paderborn   | http://ag-kastens.cs.upb.de/jwolter
  Fakultaet EIM/Informatik | Office: F2.303
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