Digital BW, The Print

I would like to try assigning a cool to the shadows 
> and a warm to the highlights sometime.


John,

you can do that in a profile easily with IJC without the
use of alpha channels. I am sure you can put a profile
together in QTR as well that does "cross" toning.

The purpose of the alpha channel control in the
PC version of OPM is for more sophisticated
control: you don't need it to assign a color by 
gray values (i.e. highlight, midtones etc) but
by specific image elements. 

You can mask out an object in the photo and
assign a profile to it. You can make a blue sky
or a red apple in the middle of a grayscale
print if you are using a full cmyk inkset.
That kind of thing.

Antonis