For digital photographs it is possible to add or update the "exif" information. Under Linux the tool is
exiftool(1), those of you still on Windows will have to find an equivalent!
I use a short script that enables me to quickly add focal length (needed for manual lenses), apperture (ditto), a short sentence and the coordinates (lat/long). Couple that with the date/time info and even my old brain gets kicked into life. Not much help I know if you are simply scanning in slides, prints or negs.