How many dpi scanner is enough to scan old photos from a soap dish?

Question

Photo

I want to scan old photos, I have a 600x600 dpi scanner, so I think it makes sense to look for more dpi or will there not be an increase in quality there?

Answer 1

Up to 2400dpi the difference is noticeable, especially on b/w film.
Ok, even if the soap dish is quite primitive, then 1800dpi.
You just need to scan not with a flatbed, but with a film and slide scanner.

Answer 2

no has not. 600 is enough