Digital BW, The Print

Hello list,
 
I know that replying to my own post it's probably bad netiquette, but my
questions went unanswered and I don't give up easily :-)
I actually tried to practice what I preached, and started out by creating a
duotone set in Photoshop with black and the usual three shades of gray (25%,
50% and 75%). I wrote the 4 corresponding curves so that:
 
1) The 4 grays were (mostly) separated.
2) Changing the image mode from grayscale to duotone using this set has no
visible effect (I used a 21-step grayscale to check this).
 
Then I wrote another duotone set using the same curves but replacing the
three grays with 100% Cyan, Yellow and Magenta, hoping to have the printer
driver replicate the behavior of the gray set (i.e., output the same B&W
image I saw on the screen and separating inks).
The funny part of it is that I'm OUT OF INKS (argh!) and therefore can't
print to see whether I completely wasted my time or not. I think it may
(should?) work, yet the color image I get when I apply my CMYK quadtone set
is very different from the one I get when applying Brandin curves, and that
is not encouraging.
This workflow would obviously work only for 4-inks printers, but has the
advantage of being WYSIWYG and being independent from the ink positioning,
since you can switch the CMY curves accordingly.
Any advice? Anyone wishing to give it a try and let me know while I wait for
MIS to have Full Spectrum cartridges available? I could easily send the
quadtone settings (maybe off-list).
 
Alessandro Pardi

 -----Original Message-----
From: Alessandro Pardi [mailto:alessandro.pardi@...]
Sent: giovedì 4 ottobre 2001 18.51
To: 'DigitalBlackandWhiteThePrint@yahoogroups.com'
Subject: [Digital BW] WYSIWYG separation curves (Was: Ink Color Equal To
It's Shade Cou nterpart part 2)



 <snip>
Do you think that using a quadtone set with
CMYK colors (i.e. picking black, cyan, magenta and yellow as the 4 colors
that compose the image) has any chance to actually result in the curves
defined for each color being used for the correspondent inks by the printer
driver?
If the answer to my last question is yes, this would provide a way to write
WYSIWYG separation curves, although only for 4 ink printers, with the
following steps:
1) Write separation curves using a CMYK quadtone set in Photoshop. These
will be used for printing.
2) Create another quadtone set with exactly the same separation curves, but
using black and 25%, 50% and 75% gray. Once you have a satisfying image with
this quadtone, apply quadtone 1 and print.

Am I dreaming?




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--- In DigitalBlackandWhiteThePrint@y..., Alessandro Pardi <
Alessandro, I'm sorry no one has picked up on this thread. I guess I 
haven't because I'm not quite sure what to say about it. I've stayed 
away from Photoshop's duotone modes because they don't seem to relate 
to anything meaningful when actually printeding. I'm pretty sure the 
image will be converted to RGB before printing and your ink 
separations will be messed up.
I think you will find you can do presisely this same kind of the with 
CMYK ink setups in Photoshop. The exact colors of the inks can be 
entered, as well as their dot gains. THe quadtone will be represented 
on the monitor and if printer with a CMYK RIP, will print the CMYK 
file precisely. The are also ways to make the Epson driver print the 
CMY properly, but K gneration control will be take from you.
Tyler

Tyler,
 
> Alessandro, I'm sorry no one has picked up on this thread. I guess I 
> haven't because I'm not quite sure what to say about it. 
 
That you're not sure what to say is already good news - I'd expect you or
Paul or Dan to pop up and say "Nah, I tried it - no way".
 
> I've stayed away from Photoshop's duotone modes because they don't seem to
relate 
> to anything meaningful when actually printing.  
 
Yet Jerry has succesfully used them for sepia printing.
 
> I'm pretty sure the image will be converted to RGB before printing and
your ink 
> separations will be messed up.

I'm sure, too, that the image will be turned to RGB before printing:
actually I do it myself to see if it changes somehow from the way it looks
in duotone mode - and it doesn't: more good news (what I mean is that if I
obtain the same RGB image using duotones rather than RGB curves, I should
get the same print).
The most recent weird thing that I found is that in the purge file on the
MIS site there is an image for each of the CMYK colors, yet the colors are
*not* pure C, M and Y: here follows the values in both RGB and CMYK mode:
 
"Cyan" = RGB(0,0,255) = CMYK(100%,79%,0%,0%)
"Magenta" = RGB(190,0,150) = CMYK(38%,89%,0%,0%)
"Yellow" = RGB(255,255,0) = CMYK(0%,11%,93%,0%)
 
Given that these image should be used to purge the correspondent ink, I
assume, if they're right, that if you want the Epson driver to print using
only the ink in the cyan position you actually have to feed it pure blue. As
soon as I'm back home I'll try to use these settings to see if I get an
image that's at least similar to the one produced by Brandin curves.
 
PS - It's all a bit frustrating: I can't print, because I'm out of inks, and
it makes no sense to scan, because I'm waiting for a Canon FS4000 (in
backorder - dammit!), so why bother scanning anymore with my LS-30?
 
Alessandro Pardi
 


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