Digital BW, The Print

Kevin,

looks like you got your answers already. But here is some food for thought:


 
> 1. Does this gamma or ramp rate change depending on Dmax?  The rate at
> which denisyt changes near the Dmax point needs to be steeper with a
> larger Dmax - I think?


That's the reason IJC made the linearization gama variable. It's an easy way
to compensate for high dmax media and inks. With profiles that result in
dmax around 1.6 the slider is set to -6. However if you profile something
with a dmax of 2.4, you will inevitably have an overall darker scale if you
leave the slider at -6.  As you go down to -11 or -12, you are in essence
lightening the mid tones. This is much like lightening the mid tones in Photoshop: 
it decreases contrast in the highlights and increases it in the shadows (as you
note above). 



> 
> 2. Is it possible to create a gamma or ramp rate which matches a
> hardware calibrated monitor at some specific gamma (1.8 or 2.2 or
> whatever)?  Is that undesirable for some reason?

I'm sure it is possible, and rather desirable, but that's not how IJC is
set up.  It so happpens that with the Lin. slider set to -6 and dmaxes
in the 1.6-1.8 range it comes pretty close to gamma 1.8 (except the shadows
look a little too light). To really match to a monitor you'd have to
linearize by hand (trial and error) with the present version. If we are
lucky enough to have a future version where you can control the
aims, it would be a matter of writing a set of aims of your choice
to which IJC will linearize your profile. That would be far more
desirable than the simple pull of the midtone we have now.



> 
> 3. Is there a "formula" based on human perception that can be used to
> determine what an optimal greyscale ramp would look like?

There may be, but I don't know it. Kodak literature has densities for
optimal grayscales as they apply to their instruments and that became
the basis for the aims in IJC. But I am sure the committees who wrote
ICC specs and gammas etc for color management have arrived at
optimal grayscales in lots of other ways. There is also the old prepress
school of dot percent where 50% means half the dot is black and
half is paper-white. 


Hope this is helpful....



Antonis