Lex Jenkins , Oct 02, 2005; 06:01 a.m.
If you scan a b&w negative in RGB and split the channels into separate red, green and blue, you'll immediately see the difference. Not only is overall tonality dramatically different, so are noise and grain.
Scanning in RGB gives you more options to finesse the final output.
For example, you can selectively use noise reduction or grain reduction techniques, as well as sharpening and other adjustments, on just one channel rather than all three.
In other cases you may find that printing from just one channel produces the results you want.
Even if you decide to reduce the final image to grayscale, you will still get some benefits from making adjustments on the RGB scan.