Re: Any plans for an active color management?

[Henning Hraban Ramm <hraban@fiee.net>]

Hi juh,

it doesn’t make sense to use device profiles of any printshop, since all the printshops in most of Europe are supposed to standardize on Euroscale CMYK (ISO Coated FOGRA##) while in the USA they use SWOP CMYK and in Japan their own standard. So you can stay with the same profiles as long as you stay on the continent.

The main difference in CMYK profiles is in relation to the general kind of paper: coated or uncoated or maybe newspaper / web offset.
(Web offset = Rollenoffset, no relation to the www / Coated = gestrichen, Bilderdruck / Uncoated = ungestrichen, Werkdruck/Naturpapier)

The difference between FOGRA27 and 39 is marginal, AFAIK. Use the latter.

If you use properly profiled RGB images, the printshop’s workflow software should convert them properly and consistently.

Conversion of CMYK colors (e.g. Euroscale to SWOP) is a serious problem, though. AFAIK the separation method (UCR/GCR) is not part of any standard.
Often I want some device dependent CMYK tone (like deep black: 30/0/0/100); if you convert that via L*a*b (even back to the same profile) you might get a 4c tone that’s harder to print and might look less clean, even if the measurable hue is the same.

That means you should keep your photos in (profiled) RGB. Probably best use sRGB to stay device independend, because that’s default for monitors, even if printshops like Adobe RGB or one of the profiles that shrink the RGB color space to printable colors.

For type and logos I still rely on (device dependend) CMYK colors and my experience how they’ll come out in Euroscale printing.
For an international project that should print the same e.g. in the US, in Europe and in Japan, I’d use differently defined graphics or Pantone spot colors. (I guess Pantone is the one spot color system that will work world-wide, even if HKS is still usual in Germany and Toyo in Japan.)
It could also work to use spot colors and have the printshop convert them to “their” CMYK profile.

Colors that you define in TeX or Metapost are a different problem. I *think* they should use the output intent as their profile. But I don’t know if the intent option of \setupcolors and/or \setupbackend really works this way. (My only means to check was Acrobat Pro 9, and that won’t run on a current macOS any more.)

Hope that helps a bit and doesn’t confuse you more…

Color management *is* hard.

Best, Hraban

> Am 2020-02-17 um 15:03 schrieb Jan U. Hasecke <juh+ntg-context@mailbox.org>:
> 
> Hi all,
> 
> I would like to come back to a discussion from 2018 on this list.
> 
> After printing some flyers for my cooperative I come to the conclusion
> that color management *is* very difficult.
> 
> In my eyes, the only way of getting good results seems to be the
> following process.
> 
> My starting point are RGB colors as we are doing online first.
> 
> So if I create a poster or a flyer I have to do this:
> 
> 1. Decide which print shop will print the material.
> 
> 2. Download and install the color profile for this print shop in ConTeXt.
> 
> 3. Specify CMYK values by using transicc with the given profile
> 
> 4. Define named corporate colors with these CMYK values for typography,
> colored background in ConTeXt.
> 
> 5. Convert all RGB images to CMYK using the given color profile
> especially if they contain corporate colors.
> 
> Now if we decide to use another print shop, the whole process has to
> start again. The result is that I end up with color settings for x
> different print shops and cmyk images for x different print shops.
> 
> Are there any plans to automate these steps into ConTeXt? That would
> enable us to work in RGB the whole time. Only when creating a print pdf
> we would specify a color profile and ConTeXt would do the rest by
> converting all rgb values to cmyk values due to the given color profile.
> 
> As this seems very complex I fear that there are no plans to do this.
> 
> What alternatives I have?
> =========================
> 
> What if deliberately define my own cmyk values once and for all?
> 
> Can I work with the same cymk values no matter what profile is used by
> the print shop?
> 
> TIA
> juh
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