I’m embarking on a project to scan our family’s old collection of slides. My plan had been to write descriptive information about each slide (e.g., when/where/why it was taken, who's in it, etc.) to the three description fields (Exif Image-Description, IIM Caption-Abstract, XMP dc:Description) in a bid to (1) ensure consistency between these fields and (2) make the information visible via as many programs as possible.
Carl Siebert's excellent article summarizes the varying ways different programs read and write the description fields (note particularly how Windows File Explorer reads only the Exif field), and Capture One's help page indicates that the IIM Caption-Abstract field is limited to 32 characters.
I don’t anticipate writing giant amounts of information per slide, but length restrictions are troubling, especially if they're as small as 32 characters. I’m concerned that if I write a description longer than 32 characters and store it in the three description fields, it will be truncated in the IPTC Caption-Abstract, but not in the Exif or XMP description fields, thus giving rise to the inconsistency writing to all three fields is intended to prevent.
I’d be grateful for advice regarding the best way to store general free-form descriptive metadata for scanned images. My slide scans will be distributed to family members with varying levels of technical sophistication using a variety of devices and software. I want to maximize the likelihood that the metadata I store will be visible to everybody, both now and in the future.