Digital BW, The Print

Robert's reply on the messages is as follows:

I went through the same sort of adjustments for the SC 980.  I
   found that printing a smooth (1%) gradient with a single ink
made
   it much easier to judge whether the dot size values were
   correct. This is because it is not transitions between inks
that
   are the issue here, but instead the transition from one dot
size to
   the next (within each ink). In other words a gradient with
only one
   ink will show the "hitches" just the same.  After changing the
dot
   values, the single ink gradient looked smooth and then the
full ink
   set fell right in line.

Agreed.  That's how I calibrate printers.


    I did the experiment of printing out a 0.45 version
   of the 21Step.tif stepwedge included in the QTR distribution.

   There's an improvement, but it is extremely subtle, even held
up to
   a very bright light. The 0.45 ramp is just a _little_ smoother
in
   the 50% and 80%-90% range. Thinking that might be natural
variation
   from print to print, I printed it again and got the same
   result. All three stepwedges (0.46, 0.45 #1 and 0.45 #2) were
   printed with the same sheet of paper, with the same carts.

   So 0.45 wins for my setup. But wow it's subtle.


OK, we'll stay with 0.45.

   This is probably within the variability of the printers, the
   measurements and the dithering code.  I re-looked at the data
and
   graphs where I came up with 0.46 and 0.45 looks just as good
(the
   two dotsize curves intersect in slightly different locations).
It
   would be nice if the gimp-print guys had a standard for
measuring
   this because other printers are way off.

I'm working on a technique for doing this.  I know other printers
are
off; if people want to tune them, I'll be happy to accept the
revised
parameters.

-- 
Robert Krawitz
<rlk@...>

Transferred by Ernst