Viltrox/Lensfun problem

Software darktable
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Hi,

I have a strange problem with darktable or lensfun. I have a Viltrox 16 mm lens, lens ID: “Viltrox AF 16/1.8 Z”. There is already this lens included in lensfun database, Sony version: “Viltrox 16mm F1.8 FE”. Even if I manipulate misc.xml to exactly match this string, darktable shows “unknown lens”. And correction does then not work.
The only workaround so far is to keep the original misc.xml and then manually select “Viltrox 16mm F1.8 FE”.
This matching however should work and I don’t know why it does not. Does anyone know?

1 Like
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Is it possible, that the available correction data is intended for a different crop factor, i.e. sensor size? This could lead to such effect.

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Both have crop factor of 1.0.

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Hm, OK. So might perhaps be a problem regarding the lens ID. I would suggest to do a search on “lensfun exiv2” in this forum, as there are quite some topics with respect to lens recognition issues. You may always override lensfun using an exiv2.ini (Windows) or .exiv2 (Linux) configuration file (there are also quite some topics covering that) as long as the the software has trouble to recognize the lens. So I assume, that this issue will be solvable.

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exiv2 -pa --grep lens/i Z6B_1842.NEF 
Exif.Nikon3.LensType                         Byte        1  (0)
Exif.Nikon3.Lens                             Rational    4  16mm F1.8
Exif.Nikon3.LensFStops                       Undefined   4  0
Exif.NikonLd4.LensIDNumber                   Byte        1  0
Exif.NikonLd4.LensFStops                     Byte        1  F0.0
Exif.NikonLd4.LensID                         Short       1  2820
Exif.Photo.LensSpecification                 Rational    4  16mm F1.8
Exif.Photo.LensMake                          Ascii       6  
Exif.Photo.LensModel                         Ascii      65  Viltrox AF 16/1.8 Z
Exif.Photo.LensSerialNumber                  Ascii      11  0

At least with .exiv2:

[nikon]
2820=Viltrox 16mm F1.8 FE

It does not work.

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Share the raw file and we can try to troubleshoot.

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Have you resolved this issue? I have the same problem with pictures taken with Nikon z6ii and Viltrox 16mm. Darktable does not recognise the lens and when I try to apply the lens correction module I get the issue “camera/lens not found”. I don’t even find this len in the drop down.

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hi @Jani and welcome! Have you tried the process outlined in this thread?

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Same problem here with Viltrox AF 20mm f/2.8 Z. I can manually apply it but DT will not find it automatically.

exiv2 -pa --grep lens/i rollosalen-udstilling-1.NEF
Exif.Nikon3.LensType                         Byte        1  (0)
Exif.Nikon3.Lens                             Rational    4  20mm F2.8
Exif.Nikon3.LensFStops                       Undefined   4  5
Exif.NikonLd4.LensIDNumber                   Byte        1  0
Exif.NikonLd4.LensFStops                     Byte        1  F0.0
Exif.NikonLd4.LensID                         Short       1  2822
Exif.Photo.LensSpecification                 Rational    4  20mm F2.8
Exif.Photo.LensMake                          Ascii       6  
Exif.Photo.LensModel                         Ascii      65  Viltrox AF 20/2.8 Z
Exif.Photo.LensSerialNumber                  Ascii      11  0
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Hi @mir and welcome! Have you made the exiv2 config file as detailed in this thread?

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I am sorry but I see no where it this thread a description on config files releated to exiv2?

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It’s the link shared by @MStraeten: User's portal · darktable-org/darktable Wiki · GitHub

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$ cat ~/.exiv2
[nikon]
2822=Viltrox AF 20/2.8 Z

2025-08-05_03-08
2025-08-05_03-08266×218 9.99 KB

So as others has said it does not work.

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Flatpak? which version of dt?

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Yeah, I’m afraid we really might have a bug w/ native Z lenses in exiv2 - there is no substitution mechanism via the config file, and the unknown value is not parenthesized so dt can detect and fall back to something else (i.e. Exif.Photo.LensModel).

See Indicate no translation for Nikon lenses by kmilos · Pull Request #3239 · Exiv2/exiv2 · GitHub. Not sure if/when this’ll get ported back to 0.28.x branch or released…

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Btw, I believe the image information panel on the left does show these lenses as “Viltrox AF 16/1.8 Z” and “Viltrox AF 20/2.8 Z”, no? So exiv2 and dt seem to do their job, i.e. the fallback works.

Thank Viltrox for not putting in consistent strings between mounts (Sony E/Nikon Z/Fujifilm XF) so they can be leveraged consistently by Lensfun. The way things are, I think one workaround would be to locally hack your misc.xml so the <model> matches the Z-mount strings. You’ll have to do it every time you update the db, or perhaps create copies of the lenses you own in a new file in your user config (e.g. $HOME/.local/share/lensfun/viltrox.xml) for a permanent change.

Also, ask Lensfun to implement an aliasing mechanism.

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dpkg -s darktable
Package: darktable
Status: install ok installed
Priority: optional
Section: graphics
Installed-Size: 33420
Maintainer: Debian PhotoTools Maintainers pkg-phototools-devel@lists.alioth.debian.org
Architecture: amd64
Version: 5.0.1-2