The PDFs produced by the collection extension include a section with credits and licenses of the images included.
EXPECTED
The names mentioned there correspond to the users that have uploaded that image of any previous version in the same page.
ACTUALLY
In addition to the uploaders, all the editors of the page are included as well. At the end it is impossible to know who uploaded the initial picture and potential updates, and who simply added a translation or a template. This is a mis-attribution.
You can test this here:
https://ca.wikipedia.org/w/index.php?title=Usuari:Pere_prlpz/taller2&oldid=12992460
Fitxer:Can Manent Premià de Mar.jpg (...) Contribuïdors: Deosringas, Isidre blanc, Pere prlpz, Vriullop
Fitxer:L'Amistat Premià de Mar.jpg (...) Contribuïdors: Deosringas, Isidre blanc, Pere prlpz, Vriullop
In both cases Deosringas is the only uploader.
Version: REL1_22-branch
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=28064