Is a classic analogue printed film photo CMYK?

Getting to your ultimate question about the gamut to use for scanning photos.

The short answer is that yes, it can make sense to scan photos with a wider gamut than sRGB. Modern printers can definitely print colors that fall outside of sRGB (in fact, a fair number even exceed the range of AdobeRGB 98).

The only real question then is what colors you have in the prints you're scanning. That varies drastically.

• If you're starting from something taken on '80s vintage Kodacolor 400, printed at a typical one-hour photo, and not stored particularly carefully since, then sRGB is probably plenty to capture everything in the picture. Newer films are generally better, but some one-hour printers have gotten even worse, so newer prints aren't necessarily a lot better.

• If you're scanning something like carefully stored, top quality Cibachrome (aka Ilfochrome) prints, then you'd almost certainly want to use at least AdobeRGB. If it were up to me, I'd do everything I could to be sure nothing was lost--which for color space would mean using ProPhoto RGB, and 16 bits per channel. Then, once it's captured you can try to figure out whether everything you've captured falls within AdobeRGB 98, and if so convert to that (and 8 bits per channel, so the files suddenly get quite a bit smaller). But I'd do my best to capture everything first, then see if it'll all fit in a smaller color space.