I had the same problem on my Nikon when I bought a
Tokina 24-70mm F2.8 AT-X Pro for it. The issue is that the camera
doesn't recognise the foreign lens and so does not populate the
necessary exif fields with the lens data. It's not a Darktable
issue.
This is my understanding of the situation.
The camera gets an id number from an attached lens( '141' in your
case, '137' in mine) and uses it to look up the lens data in it's
internal table which it then includes in exif makers data in a raw
file. Darktable (and many other photo apps) use exiv2 to query the
exif data in a raw file and exiv2 returns the data as set by the
camera. However when a Nikon (and maybe other makes) identifies a
foreign lens it seems to allocate an arbitrary id and marks it
'Unknown (8D 54 68 68 24 24 87 02)' in exif. This is what exiv2
reports to the application. This means Darktable has no data
which it can use to process the lens - so can't lookup the lens in
lensfun for correction info.
It's a camera manufacturer issue that manifests in exiv2, and is
discussed here https://dev.exiv2.org/boards/3/topics/2782
and described by exiv2 developer here: http://dev.exiv2.org/projects/exiv2/wiki/Lens_Recognition_in_Exiv2_v026_(and_later)/
While you will be able to manually select the lens in Darktable
Lens Correction module, I unfortunately couldn't because the lens
wasn't in lensfun. At first I tried to use other lenses correction
data but this wasn't satisfactory so I calibrated the lens, which
is now in the latest lensfun db. I still had to manually select
the lens in Darktable of course - which is a real pain if you
process lots of images because you can't use an automatic preset
to apply Lens Correction.
You will note the exiv2 fix is only
available for exiv2 0.26 on. As of early 2020, I found hardly
any Linux distros that had/were planning to upgrade to that
version - OpenSUSE was one, I think Fedora the other. Therefore
there may not be much you can do about it. Upgrading exiv2 on a
distro . You may be able to upgrade exiv2 to 0.26 on your
platform and recompile Darktable to use it, but that will
break any graphics package that depend on the pre-upgrade
exiv2 version - which may or may not be an issue for you.
I also lost the ability to add lens info to final image
files. I scripted a workaround for this using exiftool to look for
the bad id ('137' for me) in the LensID exif tag and then wrote
the Tokina data into the LensMaker and LensModel tags. This won't
help the Darktable issue, however.
Fortunately, I recently replaced my laptop with a workstation on
which I chose to run OpenSUSE which as default has exiv2 0.27, so
I can now use the workaround described in the exiv2 link, and the
problem is solved.
Good luck
On 15/06/2020 21:39, Michael Rasmussen
wrote:
Hi all,
Weird problem in Darktable where lens is not found although there are
lens corrections available in Darktable for the specific lens.
Darktable recognizes the lens as '141'
Hardware:
Nikon D600
Tokina 100mm F2.8 MACRO AT-X M100 PRO D
Software
dpkg -s libimage-exiftool-perl
Package: libimage-exiftool-perl
Status: install ok installed
Priority: optional
Section: perl
Installed-Size: 20932
Maintainer: Debian Perl Group
Architecture: all
Version: 12.00-1
this is darktable 3.0.2+9~g5ac2260e3
copyright (c) 2009-2020 johannes hanika
darktable-...@lists.darktable.org
compile options:
bit depth is 64 bit
normal build
SSE2 optimized codepath enabled
OpenMP support enabled
OpenCL support enabled
Lua support enabled, API version 5.0.2
Colord support enabled
gPhoto2 support enabled
GraphicsMagick support enabled
OpenEXR support enabled
Linse info from exiftool
Lens Type : D
Lens: 100mm f/2.8
Lens ID Number : 141
Lens ID : Unknown (8D 54 68 68 24 24 87 02)
Lens Spec : 100mm f/2.8 D
As can be seen Darktable uses 'Lens ID Number'.
Rawtherapee 5.8 correctly identifies the lens.
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