Digital BW, The Print

Hi Roy,

> There isn't any frequency that's not covered -- the issue is the
> SHAPE of the frequency response curve.  Using a colored
> filter at picture taking time, you can very selectively choose a
> response curve based on the film and the colored filter.

That curve is made up of frequency vs energy, and what is modified are only
frequency and energy, since that is all there is.

> However if you take the picture with color film you've reduced
> the spectrum information to just 3 values RGB and the
> response curves for those 3 values are fixed.

Again, what frequencies are not represented by the 3 RGB values that are
available on Tri-X?  The response curve can in fact be modified (mapped), so
I'm not clear why you believe it's fixed...

> With channel
> mixing you only get to pick percentages of those fixed
> response curves -- NOT simulate or duplicate the SHAPE
> of an arbitrary colored filter response.

I don't care about channel mixer.  You CAN using a tonal curve adjustment
tool, remap the color values to be any response curve you want, within
reasonable bounds of course.

> The whole concept is very simple.  In the real world visible
> light is a continuous spectrum of light frequencies with
> arbitrary amplitudes for each frequency.  Conversion to RGB
> is reducing an essentially infinite number of possibilities to
> just 3 numbers.

I disagree.  You are reducing a frequency and amplitude of a 2D visible area
to three numbers when you convert it to RGB, and to one number when you
convert it to B&W.  The frequency and amplitude are only two numbers, and
correspond to that one point.  Again, what frequency/amplitude that is
visible to Tri-X can not be represented by the three RGB values?  It's a
simple question.

If you can't demonstrate what I ask above, then your belief, and Anthony's,
is simply wrong.

Austin