Digital BW, The Print

Austin writes:

> ... it is therefore quite deterministic to
> produce a mapping from the information on the
> color film, as produced by it's spectral response,
> to the same spectral response that B&W film does.

Absolutely ... but this presumes that you have the original complete
spectrum to work from, not just RGB values.  Once the color film has
converted this broad spectral response to three RGB values, a conversion to
B&W based on this correlation between curves is no longer possible.