Find missing files but with same file name

[rikona]

I lost some photo files, possibly doing backups because they have the
same file name as a different photo. In this case pc050049.jpg is NOT
the same pix as pc050049.jpg, for example. Pictures that I know I had
[I have a print :-) ] at an event are missing.

I have many archive disks, CDs and DVDs with perhaps a hundred or so
large dir trees of archived pix.

What I'd like to do is find archived pix that may have the SAME file
name as a current pix, but are DIFFERENT pix. Given MANY archives, is
there an efficient way to do this in Ububtu? About 20,000 current pix
to process.

And, I'd also like to see ones with different names that are in the
archives but not in the current pix file trees.

Thanks,

rikona