[stevebarnes]

Wow. Thank you so much did the result. This has really been bugging me,
and I couldn't find an answer. I'll give it a try. I think I have LensFun already installed in my Ubuntu box (Ubuntu Studio, but with Gnome installed over the top), but it's the database update and the link to Darktable that has completely mystified me!
.

Torsten Bronger, the lensfun library author, has included a script in the past couple of versions of lensfun that one can run to update the lensfun data. On my Ubuntu 17.04 box, I had to do the following from a terminal:

1) Install liblensfun-bin:

sudo apt install liblensfun-bin

2) run the installed update script:

sudo lensfun-update-data

This downloads and installs the latest lensfun updates from the parent site. If you find your lens is still not yet supported, check here:

Lensfun

Jack