Digital BW, The Print

Hello All,

I have good news about the Great Paper Chase.  All of my comments are
in relation to Black Only, so you'll have to adapt this to your
workflow.

I printed Pauls's enhanced wedge on HWM (Epson Heavyweight Matte -
should we call this HWM or EHM?) with front and back end profiles at
Dot Gain 20%.  I compared the pure black to the pure black on an EAM
version of the wedge and found it was just as black.  However, the
scale was very different.  The HWM held off and didn't get to a good
black look until much later.  This means that pixels that are an RGB
value of, say 2 (which is about 94.8%), will look black on EAM but not
on HWM.  In addition, the HWM held off on going to white in a similar
manner.  The general overall effect with an image that looked good on
EAM is poorer contrast and less Dmax.  But the Dmax, and the white, is
actually there if we can get to it.

I compared the two gray scales and found that at 40-50% they match. 
Below 40% the HWM stayed darker until the very end, then suddenly
going white at about 2%.  Above 50% it stayed lighter than EAM until
dropping off into black more abruptly at about 98%.  This means that
even an RGB 1 pixel (97.4%) won't look really black.  EAM starts
dropping off at about 96%, which is much more forgiving.

I found that I could correct for this with a Transfer Function curve.
I printed another wedge and got a nearly identical gray scale as the
EAM.  I then printed my test print with it and it looked nearly
identical to the EAM print (actually a bit better).  So it's just a
matter of adjusting the output a tad.  The Dmax is there.  Here are
the curve points I used:

 10% - 8
 90% - 92

Front end profile was DG-20, Color Management was Same As Source.

I am assuming that the same can be done for EEM - can someone verify
this?  

Boy am I relieved.  This means I can use HWM (even cheaper than EEM)
for proofing just by tacking on this curve during workup, then
removing it for PR prints.  I'm a happy camper.

Regards,
Clayton


Info on black and white digital printing at    
http://www.cjcom.net/digiprnarts.htm