Canon FS4000US - grain or noise?

[John]

Scanning slides or negatives at 4000 dpi on this scanner - as I zoom in I
lose detail in multi colour speckly effect. How can I tell if this is film
grain or noise/problems with the scanner?

 

[Bart van der Wolf]

Scanning slides or negatives at 4000 dpi on this scanner - as I zoom in I
lose detail in multi colour speckly effect. How can I tell if this is film
grain or noise/problems with the scanner?

Make two identical scans of the same crop. The difference is (almost
exclusively) noise.

Bart