I generated vignetting correction data for EF300mm f/2.8L IS USM +1.4x III. darktable doesn’t find the right lens. Where did I go wrong? My guess is that it grabs LensType instead of LensModel.
$ exiv2 -pt 20210820_MG_0263.CR2 |grep -i ‘lens|model|make’
Exif.Image.Make Ascii 6 Canon
Exif.Image.Model Ascii 13 Canon EOS 6D
Exif.Photo.MakerNote Undefined 68236 (Binary value suppressed)
Exif.MakerNote.Offset Long 1 996
Exif.MakerNote.ByteOrder Ascii 3 II
Exif.CanonCs.LensType Short 1 Canon EF 300mm f/2.8L IS
Exif.CanonCs.Lens Short 3 420.0 mm
Exif.Canon.ModelID Long 1 EOS 6D
Exif.Canon.LensModel Ascii 74 EF300mm f/2.8L IS USM +1.4x III
Exif.Photo.LensSpecification Rational 4 420/1 420/1 0/1 0/1
Exif.Photo.LensModel Ascii 32 EF300mm f/2.8L IS USM +1.4x III
Exif.Photo.LensSerialNumber Ascii 11 0000000000
I suppose that darktable displays somewhere the name of the lens that it finds or decodes with exiv2 in the metadata and use to fetch it in the Lensfun DB
The reason I haven’t used that feature it that the lens recognised is 300/2.8L IS USM without teleconverter 1.4 III.
I will play around with the settings. I also own teleconverter 1.4 II to try. Didn’t have any problem with 1.4 II before so I shouldn’t have it now either.
What I found is that in darktable it was searching for the name Canon EF 300mm f/2.8L IS
I changed slr-canon.xml from EF300 f/2.8L IS USM to Canon EF 300mm f/2.8L IS and that one works now. So it reads LensType and not LensModel.
x1.4 II and x2 III worked before but now none of the three converters are identified.
In this case it will be me who sends the data to Lensfun. If it doesnt work for me it will not work for others. If this would be about another lens already in Lensfun, then .exiv2 would be the best solution for just me.
With that said my biggest issue is still that I can get one of the four combinations to work, but not four.
Nothing new there. Try yourself with my raw files. The issue here is extenders. Not a single lens. A single lens is easy and that is what you have been linking to all the time.
It seems .exiv2 is not created for a lens with different extenders so the walk around most be something else. Why, for example, is not darktable reading the tags LensModel? A bug?
Tried with my 200/2.8L IS USM II. It works differently. LensType changes with the extender. Well, not for +1.4II and +1.4III. It means that it in this case would be possible to use .exiv2 to point it right, but only to choose one +1.4