Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Anthony 
Atkielski" <anthony@a...> wrote:
> Peter writes:
> 
> > There's no reason why that should be true.
> 
> There's an excellent reason why it is true, which I've just 
explained in a
> separate answer to Seth's post.
> 
> The only accurate B&W you can get from an RGB image 
> is "perceptual" B&W that precisely matches the spectral
> sensitive of the RGB capture device in the first place. 

Not if you're scanning black and white film.   The shape (N.B., the 
shape, not the translation) of the histogram will be the same in all 
3 channels of your scanning device.   All you need to pick the one 
that gives you the best S/N ratio.   That shape, furthermore, 
reflects the spectral sensitivity of the film, not the scanning 
device.   For instance, if the b+w film in question is pre-
panchromatic it will tail off on red subjects.  But it will do so for 
the R,G, and B scanning elements.