Apologies if I am doing something wrong - I do not read German.
When an image is open in the viewer, and I press F2 to bring up the dialog box to rename the file, the rename is not successful if it only involves a change of case in the letters. (This happens either way, from lower case to UPPER CASE or vice-versa.
Thus, if I try to rename
(de) SSB 3045.jpg to "(DE) SSB 3045.jpg"
the file name remains unchanged.
Any other change is accepted.