Comment 4 for bug 256875

To skip the Canon tags is quite an unsatisfactory workaround. I have temporarilly used a wrapper aroumd the exiv2 command line tool and I never had the problem of copying the exif keys.
What I do not really understand if we skip conversion, it then afterwards cannot write the metadata. It only has to convert the ugly tuples into strings if I understand correcty. The weird things actually is that pyexiv2 after reading the metadata itself converts the stuff into tuples.
I hope Olivier can fix this soon, because it is quite a blocker.