[scribus] No real CMYK black possible??

[Tino Schwarze]

Hi Andreas,

On Sun, Jun 22, 2008 at 07:12:41AM -0700, avox wrote:

> > I'm currently designing a folder with black background. I'm using
> > the ISOCoated v2 (ECI) profile for offset printing. But my black (as in
> > CMYK=0/0/0/100) background doesn't look black at all on screen. Scribus
> > as well as Acroread display a very dark grey and I can even distinguish
> > it easily from the pictures I converted from sRGB->ISOCoated using
> > tifficc. (Pictures converted by scribus are also okay and visibly darker
> > than my supposedly-black background.)
> > 
> > I tried unchecking Blackpoint compensation - no visual difference. I've
> > set the rendering intent to "relative colorimetric" and exported to
> > PDF/X with ISO Coated v2 destination profile. I also tried PDF1.4
> > without profiles (with Printer as destination) - same result.
> > 
> > How will I get a real black color?
> > 
> > Scribus version is 1.3.3.11, running on SuSE 10.3, liblcms is 1.16.
> > 
> > I've got a workaround: made a 10x10 black TIFF, converted to ISOCoated,
> > used it as background but the print shop will probably complain about
> > too low resolution.

> CMYK 0/0/0/100 isnt the blackest black in CMYK space, so colormanagement
> maps it to a dark gray in RGB space (as used by your monitor).

Okay.

> There's also Rich Black (eg. 40/40/40/100) and Total Black
> (100,100,100,100),
> but the latter is rejected by many printers because it uses too much ink.


> In Scribus it would work best to create an RGB black (0,0,0) and rely on 
> colormanagement to convert it to the darkest CMYK black available in the
> target color space.

Hm. Something strange is happening here. Please have a look at:
http://www.spiritualdesign-chemnitz.de/tmp/blacktest.tar.bz2
It has the following files:
blackbg.tif - 10x10 RGB TIFF without any profile
blackbg-ISOcoated.tif - 10x10 CMYK ISOCoated v2 TIFF created via
  tifficc -i sRGB\ Color\ Space\ Profile.icm -o ISOcoated_v2_eci.icc -c2 -e -b -t1
schwarztest.sla
schwarztest.pdf - PDF created from sla via "Printer" PDF 1.4 export, no
profiles used
schwarztest-bp.pdf - PDF created from sla via "Printer" PDF 1.4 export,
no profiles used, but blackpoint compensation turned OFF in document
properties

The point is: The image created by tifficc is really black. The same
image converted by Scribus does not show up black in Acroread nor Scribus.
Neither do the "black" colors. To make things worse, the black from the
RGB image is not the same as the black from the RGB color! The image's
black is even lighter. If I disable blackpoint compensation, the RGB
image shows up black in Acroread. Is there a bug in Scribus or tifficc?
Since I created the ISOCoated image with blackpoint compensation enabled.

Bye,

Tino.

PS: Is there some Linux program to load a CMYK PDF and check the CMYK
values?

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