Digital BW, The Print

Peter De Smidt wrote:
> I've recently started testing out QTR, and so far, so good.  I haven't 
> found any explanation of the various dithering options, though.  Anyone 
> know what these are? (I have searched on the QTR yahoo site, but I 
> didn't find the info.)

Enough threads on the QTR list on the dithering but I 
selected one of them here, I guessed Clayton wouldn't mind:


 >>
Hello Ernst,

 > >What are the best results with QTR and BO for the 
different  Dither
 > >Algorithms ?  The effect must be more visible in BO 
printing and may
 > >vary per printer and paper. I also wonder what looks 
most alike the
 > >Epson driver in BO mode. Just curious.

I've been wondering that myself (haven't used QTR much yet, been
working only with the "Ordered" setting which is slightly
tighter/smoother than Epson) so your question made me go 
find out.  On
a 2200 w/ Eboni and my current QTR BO curve (still under 
development)
I printed a step wedge on EEM for each dither setting and 
compared
them.  All were with 2880 and "Faster" speed setting (more 
about that
below).  Here are the results:

-----------------------------------------------
Ordered - smaller patterns of dots than Epson's squigglies, 
slightly
tighter pattern, slightly smoother in appearance.

Adaptive Hybrid - tiny difference in pattern if you look 
hard for it
with the loupe, but for eyeball appearance is nearly 
indistinguishable
from Ordered.

Fast - Pretty much same as Adaptive Hybrid, but under the 
loupe I see
a tiny bit of dither banding.

Very Fast - Horrible!  Prints streaks of graphic patterns.

Hybrid Floyd-Steinberg - Surprise!  Very tight and smooth. 
Noticeably
smoother to the eye compared to Ordered and Epson.

EvenTone - More surprise.  Ever so slightly smoother than 
Hybrid FS.
-----------------------------------------------

For a more practical test to verify the above, I printed a 
landscape
with clouds, an image that has always showed up BO weakest area,
smooth midtones.  It verified all of the above ramp 
observations.
There is a place in the clouds with little swirling patterns 
that are
barely defined in Epson BO, are a tiny bit better with 
Ordered, and
are very crisp and clearly defined with HFS and EvenTone, with
EvenTone being a tiny bit the better of those.

I am delighted.  This is going to make a huge difference to 
BO lovers.
  Just on this one test print I can see it's an enormous 
improvement,
with a greatly reduced grainy look and retains the 
luminance.  Now I
just need to finish working on the curve.  It's still too 
blocked up
at the dark end.  I will post it as soon as it's done, 
probably over
the coming weekend.  Wahoo!  Imahappycamper.  Why didn't I 
try this
before???!!!!  Still need to test with other papers...

About the "Speed" setting: I printed a TrueTone ramp with 
Speed set to
"Better" (still 2880), and it messed up the ramp, 
introducing some
bumps and streaks into what had been a smooth ramp using 
"Faster"


Regards,
Clayton
<<


-- 
Met vriendelijke groeten,Ernst


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