I'm using an Epson Perfection V600 Photo scanner to scan color negatives. The scanner supports Digital ICE, which uses infrared light to scan for dust and automatically correct images to remove dust artifacts. Also, its maximum optical resolution is 6400 DPI.
I've noticed that when I don't have Digital ICE enabled, the scanner motor moves extremely slowly and delicately in 6400 DPI mode, so its stepper motors can capture a negative at that size. However, I've also noticed that when I enable Digital ICE, the motor moves quite a bit faster during the visible light scan, as if scanning at a lower resolution. (The noise of the motor clearly changes pitch based on its speed.)
After some testing, I determined that with Digital ICE enabled, the maximum speed that the scanner head moves during the visible light scan is the same as that for 3200 DPI, even with the scanner in 4800 or 6400 DPI mode. It only ever moves slower than that speed when Digital ICE is off. (With it off, 4800 DPI and 6400 DPI clearly sound unique.)
Are the images scanned at the 4800 or 6400 DPI settings when Digital ICE is on interpolated from 3200 DPI scans? Or is the scanner able to scan at 6400 DPI with no interpolation at faster speed?
I'd like an answer that objectively compares pixels on different scans using color film with low grain. (I only use the high DPI settings when scanning low-grain film, e.g. Ektachrome, Ektar, etc. and don't bother with it for stocks like Gold, Superia, etc.)