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Re: RGB-to-CMYK

Posted by Stephan Saalfeld on Jun 05, 2013; 10:18am
URL: http://imagej.273.s1.nabble.com/RGB-to-CMYK-tp5003233p5003236.html

Emmanual,

the only way to guarantee that colors are reproduced on different
devices (screen, printer depending on paper types) is to save the image
as you generated it together with the correctly calibrated ICC profile
of the device that you used to generate it (your monitor).  Regardless
what color space you use (CMYK is redundant as you most likely created
it in RGB on your screen), a device that understands the ICC profile of
the source and its own can transfer the colors accordingly.

Without these profiles, it's all hand-waving and you are actually lost
to chance.  That doesn't mean that you can't play around a bit and tweak
the outcome to your approximate needs.  But that requires that you have
access to all devices and that you do not change them.

If you want to convert to CMYK because some printing or publishing
company asked you to do it without giving you the ICC profile of their
printing device nor asking you for that of your screen, then these
people are incompetent and just try to fool you.  You cannot do it
right, neither can they.  Send them your image in sRGB and see what
happens.

Best,
Stephan



On Wed, 2013-06-05 at 11:51 +0200, Emmanuel Levy wrote:

> Dear Reinhard,
>
> Thank you for your reply - I guess this means we will have to go over each
> image and optimize it to obtain a rendering similar to that obtained with
> RGB then.
>
> Best wishes,
>
> Emmanuel
>
>
>
>
> On 5 June 2013 10:33, Reinhard Rachel <
> [hidden email]> wrote:
>
> > to my knowledge, you won't be able to get the "same color impression" - it
> > is a different "Color Space" and therefore, the result is necessarily
> > different. (and, it depends to some extent on the program / program
> > version, and to great extent, the monitor you are using: is it a calibrated
> > one? = expensive). Please correct me, if I am wrong.
> > kind regards,
> > Reinhar
> >
> > --
> > Prof. Dr. Reinhard Rachel
> > University of Regensburg
> > Centre for EM / Anatomy
> > Faculty of Biology & Preclin. Med.
> > Universitaetsstrasse 31
> > D-93053 Regensburg - Germany
> > tel +49 941 943 2837, 1720
> > fax +49 941 943 2868
> > mail [hidden email]
> > office: VKL 3.1.29
> >
> > next microscopy conferences:
> > http://www.mc2013.de/
> > MC2013 in Regensburg, Germany
> > http://www.imc2014.com/
> > 18th IMC 2014 in Prague, Czech Rep.
> >
> > --
> > ImageJ mailing list: http://imagej.nih.gov/ij/list.html
> >
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html

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