I use an extender w/my lens (Canon 1.4x). What’s the impact of an extender on lens correction? I also noticed that the exif lens field value includes the extender in it (eg “Canon RF 100-400mm F5.6-8 IS USM + RF1.4x”, which causes dt to not find the lens in the lensfun database xml file that dt includes (I can manually select the lens from the drop-down as a workaround). It seems that the dt search should be tweaked to account for that. Also, for dt on Windows how should we be updating the lensfun files as they continue to update them? Do we just pull down their XML files to the dt > lensfun > version_1 folder if we find a lens in their github xml that’s not in the xml installed w/dt?
It essentially means you have a “new” lens to correct; e.g. the correction for the lens without the extender is not the same as the lens with the extender.
The XML file directly from lensfun are version 2 of their correction spec and need to be converted to version 1 spec in order to be used in darktable.
There is a small dbupdate.exe utility provided by a member that downloads the version 1 of the database. Please search the forum.
Thanks for the feedback. Sounds like if I keep using the extender on my telephoto lenses I’ll have to do lens correction manually since lensfun will never have the combo in their db. Will the next dt release support the version 2 of their files btw?
Will do!
Well you can make your own lensfun correction if you want. It isn’t that hard.
Likely no.
It seems like the correction in Lensfun only includes the lens and only distortion. If you manually select the lens when using an extender it will be wrong.
If you just want to add distortion correction for 100-400 + extender that will be super easy. The hardest part for you will be to find a decent target.
I don’t have any RF lenses so I will not be able to create any profiles for them. The next lens I will deal with will be EF80-200/2.8L.