Re: Lost in ICC Land
Re: Lost in ICC Land
- Subject: Re: Lost in ICC Land
- From: Henrik Holmegaard <email@hidden>
- Date: Sun, 22 Apr 2001 10:55:05 +0200
Darrin Southern <email@hidden> wrote:
With the latest range of 6 color (CYMKcm) inkjets, their densities are much,
much higher than the above mentioned printing or analog proofing methods.
Henrik Holmegaard <email@hidden> wrote:
e. Some inkjet systems are four color CMYK, others six color CMYKcm with finer
highlight screening. Colorimetrically the CMYKcm printers are CMYK printers
(depending on the hue of the c and m inks). In terms of ink densities both
printer types present a CMYK interface to the world as the media chemistry is
the same. So on a six color inkjet the total area coverage is divided over six
colors rather than four causing each color to have a lower limit, except that
in the light colors more ink is put down for the same L density than in the
dark colors, so here in the light colors ink densities rise. This is handled
internally in CMYKcm inkjets.
So it follows that as I wrote:
Also the press inks and your inkjets inks have different colors. Even
the blacks are a different color.
And this is as simple as checking the primaries in ColorThink :
Also the press inks and your inkjets inks have different colors. Even
the blacks are a different color.
So far we4re saying the same thing, no? The larger elementary spot
size, the L densities of light cyan and light magenta rising in the
highlights, all this means that the inkjet is putting down more ink
for the same channel percentages compared to an offset process.
Also inkjet inks penetrate the paper and don't sit on top of the
paper the way fatty offset inks do. So we want to control densities
in very different ways. If we set the same densities on the inkjet as
on the press, and think of that as color management, then we're
breaking the workflow.
(Wrt CMYK profiles into CMYKcm output handled in the RIP, remember
that for now ICC profiles are four channel partly because of issues
over +4 channel file formats.)
'Personally', I have found that setting the ink densities, and then the
total ink limits BEFORE building the profile, is actually 80% of the work
needed, and then how you build your profile (UCR/GCR - Black generation) is
the other 20% of the work.
Of course, but you're looking at two different contexts. For the PS
DesignJets, this is preset right out of the box. The third party
proofing papers I'm playing with like MPA Sihl J35 (L97.5 a1 b-1 -:))
also work fine with these presets.
If you have a third party RIP, the ink limiting is up to you. Which
is why I wrote:
d. Density control comes before color control. Ink limiting is about
going high
to get the pure colors that outline the gamut volume, and not loosing detail
through spatial bleeding problems. Taking down the ink limit shrinks gamut and
boosts detail. Taking up the ink limit boosts gamut and shrinks
detail. Before'
the CMYK testchart is printed as deviceCMYK (no conversions anywhere), get the
ink limit right, and make it stay right.
Peter Henry at Gretag Imaging and Joe Euler at Public P3 then posted
tips on ink limiting with the PosterShop RIP.
Over on the computer to plate list, Roberto, Chris and yours truly
were trying to put the 'density control comes before color control'
message across fairly clearly this week -:).
These were the first 'TWO' documents I read on profiling, and I am still
waiting on the 'THIRD' to be finished . . . ;)
Well, it's finished alright, so I'll let Sweet Sue know you're waiting -:).