Digital BW, The Print

+> ...
> >> ... the question of "what should we really be linearizing to" 
> >> has been one of the deeper recurring questions.  I think the 
> >> fall-back to linearizing L* hasn't really been that understood.

> > I don't think this issue has quite the import you give it. 
> > Linearizing to L is done with QTR, sounds like Paul may be doing it,
 
> Paul targets his own luminance scale (linear or not).

It's linear to L for a matte paper with a dmax of 1.68.  That is, if one
makes a graph with the step wedge grayscale percentages on the horizontal
axis, Lab L at even steps on the vertical axis (the visual density numbers
that equal the Lab L equivalents would not be in even steps), then the
(grayscale %, Lab L) dots on the graph make a reasonably straight line with
the 50% point in the middle at lab L = 56.6.

Where I have diverged from Lab is that I continue to put the 50% point at
that L = 56.6 or density 0.61 no matter what the dmax or dmin.  I think this
makes for images that will print on both glossy and matte papers without
having to alter the files.  The additional glossy paper compression is
mostly in the dark shadow tones because they most often are wiped out by
reflections anyway.


> > but it's hardly a standard. 

I got there empirically based on my wanting to keep my files made for the
PiezoBW system printing consistently.  I, frankly, didn't care or even know
about Lab at the time.

Paul
www.PaulRoark.com