[scribus] Color management conclusions (was: Re: No real CMYK black possible??)

[Tino Schwarze]

Hi there,

On Mon, Jun 23, 2008 at 07:02:10AM -0400, Andrew A. Gill wrote:

> >> 3.) I tried printing separations, and I got interesting results.
> >
> > It looks like ghostscripts eats some colors.
> 
> That would not be my conclusion.  My primary conclusion would be 
> user error.

Management summary: General user error. :-(

I took my example and actually _filled_ the rectangles now. I then
exported to "Printer" PDF, converted that to CMYK TIFF using Ghostscript
(8.5) and loaded that up into Cinepaint 0.23.

I observed the following:

- CMYK colors were not altered.
- black image converted by tifficc exactly matches black image converted
  by Scribus (CMYK 87%/79%/64%/93%) - good to know, saves me a step in
  the future and lots of disk space
- black image with ISOCoated profile looks different on screen than
  black RGB image, even though they come out the same in CMYK (ISOCoated
  image looks a lot blacker on screen). IMO that shouldn't be the case.
- RGB 0/0/0 black became CMYK 0/0/0/100 black.
  -> this does not match the black image, so I cannot combine a black
  RGB background with a black RGB image for printing!
  This is not a Ghostscript issue since I checked the EPS file exported from
  Scribus - there is no cmyk color like from the image in there, only 
  "0 0 0 1", "0.4 0.4 0.4 1" and "1 1 1 1" as expected from looking at
  the TIFF.

So the only remaining issues are that "black from RGB image" does not
match "black from RGB color" when exporting to CMYK and that "black RGB
image" and "black ISOCoated image" look different on screen.

Should I file a bug report on these issues or are they known?

Thanks and sorry again for the fuzz,

Tino.

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