[argyllcms] Re: Profiling flexo presses
- From: Roger Breton <graxx@xxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 22 Aug 2005 12:03:41 -0400
Hello Jan-Peter,
> Here in Germnay the ECI 2002 Target is very succesfully used for
> profiling flexo.
> It contains 3% steps for every colorcombinations and 1,5% for pure CMYK.
I tried ECI2002 in the past with flexo presses here. Works OK except in the
highlights, especially for proofing. While it contains separate patches for
2% cyan, 2% magenta, 2% yellow and 2% black it does *not* contain patches
for 2% combinations, like 2c2m2y and so on. Instead, int contains patches
for 3% combinations which is good for offset but not critical enough for
flexo. No one I know in this industry today pretends printing 1% dot on
press so, in image pictorials, anything below 2% is simply removed.
> For getting good flexoresults the linearization incl. bumpup is the key.
This is where I loose you guys...
> The bumpup is needed to get a well defined first printing point.
If I manuall assign a 2% dot to my images I don't need anyother "bumpup" or
do I? My imagesetter is linearized to hold that 2% on film. My plate process
is calibrated not to loose that 2% dot on photopolymer plates. And the press
will print that 2% dot, albeit with gain. To me that defines a well
calibrated process. Yes, I have a choice of using or not some curves in my
imagesetter to "cut-back" the midtone dot. But I prefer NOT to do it.
Instead the profile does the cut-back for me. BECAUSE IF I DO THE CUT-BACK
ON MY FILM HOW AM I GOING TO DO MY COLOR PROOFING??? Do you see my point?
> The linearization is needed to correct the middle-tones offset-like
Does the world of offset uses cut-back curves to correct the midtone dot
growth? No. They use curves in CTPs until they reach the dot gain or density
value they want in the midtone and across the rest of the tone scale. But
that's it. That's not really a "cut-back" or "bump-up" curve for me.
> typical results file->print in germany are:
Do you mean *on film* or *on press*?
> 1%->0%
Yes, on film. I agree. On press, 1% dot disapears completely after a while.
> 2%->7% (bumpup)
Depending on aniloxes, 2% dot on plate can go up to 14% and 20%! In offset,
2% can go to 9%, depending how it's measured and managed in the CTP.
> 50%->66% (linearization for offset TVI)
There, it depends on how curves is defined in CTP. Old analog film to plate
grows from 50% to 70% to 72%, depending on the press, in my experience.
> Most flexo-printers get offset-data, which has to be converted to flexo.
Yes, and I do that through ICC profile conversion. Once the image is
converted then the operator will manually proceed to retouch the image for
1% dots, vignettes and other flexo artefacts.
> This could be solved with a devicelink from argyll. Input-data could be
> SWOP and destination-data your flexo-values.
Yes, DeviceLink would work well if only they were supported in Photoshop :(
> :-) Jan-Peter
Regards,
Roger Breton | Laval, Canada | graxx@xxxxxxxxxxxx
http://pages.infinit.net/graxx
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