[Scribus] PDF importing and colour problems
Fri Nov 9 15:56:18 CET 2007
I'm having problems with Scribus, imported PDF's (and to a lesser
extend with photos) and exporting a PDF to be printed by a printing
company. The color and overall image quality is greatly reduced in
this process. I have looked into the color management documentation
and can't really understand why scribus behaves the way it does. It
may be I have misunderstood some basic color management concepts
(since this is a new field for me), but right now I think color
management is not needed at all in my case. Can anyone shed some light
on my problem?
I deduce that I don't need any color management, since:
- all the graphical material is from third parties;
- The only modification I will do is rescaling, I will not work with the colors
- It doesn't matter what it looks like on my monitor, only the
printing result matters.
- The final product will be printed at a printing company, not by me.
The material consists of PDF's containing both graphics and images
(mostly in CMYK colorspace, though some could be in RGB), and photos
taken by just some ordinary people with a digital camera that could be
your or mine (RGB jpg's mostly).
But, if I open a PDF containing one piece of the original material,
and a PDF exported by scribus containing the aforementioned PDF, there
quality is visibly reduced in the exported PDF; colors are pale, and
dark areas are more prominently black. Particularly, skin color
becomes really pale. I have tried exporting without and with color
management (with several different profiles), and with and without
converting to process colours when not using color management. I got
the best (but still not very good) results without color management
and by converting colors to process colors. I even tried with the
Web/Screen color profile instead of Press, but neither that gave good
Also, I'm suspecting that ghostscript rasterises PDF's as RGB bitmaps
(even if they are originally CMYK), and then Scribus converts this
back to CMYK (if press setting is selected in the export to PDF
dialog). I hope this is not the case. Can anyone verify, if this is
the case or not?
Here's an example what happens to the colors, with color management
disabled. (as it should in my case?). I have a PDF that needs to be
embedded with a large area of almost the same shade of a blue; in the
original PDF the %values for the blue at a certain point are roughly:
But, after importing the PDF into scribus, and exporting as PDF (with
press setting in the color tab), and looking at the same area:
There is a HUGE difference in the overall amount of black and yellow
channel used in the picture when compared to the original. It seems
Scribus maximizes K in the cost of CMY (in this case, Y), and it
really looks bad. I got this information at the printing company (I
think we used Adobe Photoshop for comparison, tough I could be wrong
about the program, it could have been some other Adobe tool - however
I saw the effect of showing only the black channel in the original
PDF and the PDF I had exported from Scribus). The same "conversion" is
done for all RGB pictures.
I want to achieve this: all graphics should remain as is - i.e. RGB
pictures should remain as RGB pictures, and the numerical CMYK values
should be left untouched. The printing company agrees (or actually
recommended this). Is this possible with Scribus?
Thanks for the help in advance! I'll be happy to answer any questions.
Ville Aakko - ville.aakko at gmail.com
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