Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Anthony 
Atkielski" <anthony@a...> wrote:
> Peter writes:
> 
> > Why should this be so hard?
> 
> I've explained this several times.  Apparently I lack the 
necessary talent
> to make the explanation understandable.
> 
> > Every black and white film has a characteristic
> > response curve, and that curve can be characterized
> > for R, G, and B ...
> 
> No, it cannot.  The curve is just that: a curve.  The RGB values 
are just
> three numbers--equivalent to three straight lines of different 
heights in
> the spectrum.  All the rest of the curve between those three lines 
is lost
> when a picture is taken in color. 

The spectral response of both the film and the filters used in CCD 
Bayes patterns overlap (as do the photopigments in the human eye) so 
I'm not sure what you mean by "in between".  Are you saying there 
are wavelengths of light that fall between the response wavelengths 
of the color film (or CCD element filters) that the black and white 
picks up?   Could you give a specific example?


> Because of this, the original curve of the original scene 
> CANNOT be recreated from the RGB values.  And since the
> original curve of the original scene MUST be recreated 
> in order to proper render a scene in B&W based on the
> sensitivity curves of a black and white film, 

I don't know what you mean by the "curve of the original scene".  
All you need to care about is the curve(s) of the recording medium.  
That's provided by knowing the response curve of the color film in 
each channel.   I don't understand what information you think is 
missing.   You keep talking about data "in between" the R,G, and B 
values but those sensitivy curves overlap.