I’ve just become the lucky owner of the YN33mm F1.4S DA DSM WL Pro (for Sony E mount).
It’s really a great lens, but it has a quite pronounced barrel-distortion, and it’s not in the lensfun database yet.
I’ve submitted calibration-images to the lensfun project, so hopefully the lens will soon be in the database, and the problem should go away for most Darktable-users who happen to use the same lens.
However, I have to run Darktable as an appimage on my Ubuntu-machine, and the appimage version seems to use a built in lensfun database, not the systemwide one. I haven’t found a way to update it. So even if my calibration-images are accepted and a lensprofile is added to the official lensfun collection, I won’t be able to use it myself.
But - I’ve found what seems to be a great workaround:
I use two lens correction modules.
In one of them I correct with the Samyang 20mm f1.8 ED AS UMC profile,
in the other I correct with the Samyang AF 35mm f1.8 profile
and that seems to fix the distortion issue quite nicely
Here’s the uncorrected image:
Here’s the image corrected by Rawtherapee using the official Yongnuo profile for the lens
And here - my two-step workaround using Samyang profiles in Darktable
(never mind that the whitebalance in the third image is diff. from the two others, it’s not from the lens correction, it’s just me goofin’ around)
To my eye the Rawtherapee/Yongnuo correction has a slight pincushion distortion, so the double-samyang correction seems even better.
i haven’t tested what to do about vignetting and chromatic aberration, but since Darktable lets you fix both of those manually, it shouldn’t be a big problem.
So there you have it - a small tip for users of the Yongnuo 33mm f/1.4