Ability to scan up to 20MP doesn't mean that the film contains so much details though. I'm not sure of the exact resolution of film but generally, it might not be anything more than 8MP. what's the largest size you could print without degradation in quality? that would give an indication of the resolution of film.Originally Posted by theITguy
Managed to find an article that shows the results of testing of different types of film/slides. Velvia captures a lot more details than the current 6-8MP DSLR but faster positives lose out.
you can always scan higher and higher but there's only so much details in source (e.g scanning a magazine, printed around 300DPI, higher than 600dpi doesn't help extract more details). another e.g. would be digitising of sound. CD quality is sampled at ~44KHz which is around twice the range of human's ability to hear/sing. sampling higher doesn't help.