Lens correction “not found” for EF-FX mount adapter

Both the camera (Fujifilm X-E2) and the lens (Canon EF 50mm f/1.4 USM) are listed as supported in Lensfun, but their unexpected combination throws darktable off.

This electronic EF-FX lens mount adapter detects the Canon lens but adds ALSTON+ to its name:
Lens correction showing camera/lens not found

Moreover, the manual lens selection menu does not offer any Canon lenses:
Lens selection missing Canon

Can it be made to work in darktable (i.e. to let me override the camera+lens combination)? If I should file an issue, then where would it be — darktable or lensfun?

Thanks in advance for any pointers.

Do you have a raw sample?

I haven’t tried, but what if you open mil-fujifilm.xml and add a line Canon EF somewhere in the mount section? It should let you choose the lens in manual mode.

If you don’t use T2 mount you can just exchange T2 with Canon EF.

ALTSON, is that the name of the adapter? If that is the case, then you may need to copy the lens data for 50/1.4 and rename the new part as ALTSON+Canon EF 50mm f/1.4 USM instead of Canon EF 50mm f/1.4 USM.

Yes, that works, but I noticed that the parameters are not remembered by darktable and the correction is lost when the file is reverted to its original contents. I wouldn’t like to depend on modifying the file on every lensfun update, and I wouldn’t like to depend on a local copy being present in ~/.local/share/lensfun (which didn’t work under Flatpak anyway), so this is not an acceptable long-term solution for me.

On the up side, while editing the file and looking around, I noticed there is a number of “Generic” cameras which are compatible with all lenses. Once I chose the “Generic, Crop-factor 1.5 (APS-C)” camera, I was able to find the Canon lens in the lens selection menu, and that works well enough for me. Thank you for the pointer!

Sure, here is one, with the XMP demonstrating the use of the “Generic, Crop-factor 1.5 (APS-C)” camera:
DSCF8523.RAF (31.9 MB)
DSCF8523.RAF.xmp (6.6 KB)

Yes, ALTSON is the brand name on the adapter. I do not mind picking the lens manually from the drop-down, but thanks for the tip!

How often will you update Lensfun? Just put a local copy of your modified xml file somewhere in a folder. The few times you update Lensfun, just drag the modified xml file into the right folder again.

What I changed to get full auto support.