Quadtone "Working Space"
Quadtone "Working Space"
- Subject: Quadtone "Working Space"
- From: Nick Wheeler <email@hidden>
- Date: Sun, 10 Feb 2002 17:48:59 -0500
on 2/10/02 10:31 AM, Bruce Kinch at email@hidden wrote:
>
The Cone RIP must do something like this in BW, but you
>
are talking color here, right?
No this is b/w. I am not too familiar with the latest Cone stuff, for
instance I was unaware that they had a RIP and I really don't know how the
inks are being used there. I tried the "Piezography" driver and inks on an
Epson 3000 and I didn't really like the results but I really chalked it up
to operator error and moved on. I have never had much luck using what I
don't understand. Except film - that works ok for me, took a lomg time
though...
I figured there had to be a way to use a profile to correctly predict the
behavior of a quadtone setup. The key is to create a profile of the printer
as an RGB device then use this profile as an applied profile rather than a
standard "convert to" printer profile. So far here when I make drastic curve
adjustments to the red, green and blue channels to force the printer to
print only the "cyan" or light colors in the quarter tones and roll in the
darker inks for the 1/2 and 3/4 tones this applied profile gives a pretty
good indication of any posterization or banding problems that may occur.
Just print with whatever driver settings you used to create the profile.
It's like a crossover network in a speaker, you use the light inks to drive
the highs, roll in the medium inks for the middle and the dark inks for the
shadows. The curves look very similar to speaker crossover curves. Chris
Brandin has developed curves along these lines as has Paul Roark. If you
apply a printer profile to any three channel image and then load Chris'
curves it fairly well predicts their behavior. Incidentally these guys have
developed very sophisticated curves, well worth a look.
The idea is that with standard inks in the quarter tones the dots have to be
very far apart in order to properly render that light tone and you can see
them. So use lighter ink and then you can print the dots closer together (at
a higher percentage or density) so they become invisible.
In old fashioned process color quadtone printing the idea was to keep the
black out of the light areas and just create the light tones with the more
transparent CMY inks. Bruce Faser has some curves in his book "Real World
Photoshop" illustrating this process quadtone technique. These were the
types of curves used for early Iris quadtone printing.
This is a very preliminary finding - I'm throwing the idea out there to see
if it works for others. It's so absurdly simple I'm shocked that it seems
to, and I have no idea why. It is a slight variation of "forcing the screen
to look like the printer" that I mentioned in an earlier posting.
Nick
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