[Scribus] Re: Color issues in 1.1.0

[Peter Linnell]

On Sat, 2003-10-04 at 01:07, francis tohill wrote:
> This can sometimes occur if the placed image is RGB, the PDF will produce a
> very washed out result when it converts to CMYK.
> I've had this problem happen even with quark.  If that's not the problem I
> don't know what's happening there.

<snip>

This is also true. And the key word here is *sometimes*. Why some and
not others.  The color shifts will be most pronounced in colors in RGB
which are not easily reproduced in CMYK - deep blues, saturated greens.
When Scribus performs the conversion it rightly does some GCR
adjustments. 

I do recommend updating to lcms 1.11, as it has additional abilities
with black point adjustments, which Scribus will recognize and use.

Regards,
Peter


> 
> ----- Original Message -----
> From: "Peter Linnell" <scribusdocs at atlantictechsolutions.com>
> To: "Sunil Joshi" <pavansut at comcast.net>
> Cc: <scribus at nashi.altmuehlnet.de>
> Sent: Saturday, October 04, 2003 2:30 PM
> Subject: Re: [Scribus] Re: Color issues in 1.1.0
> 
> 
> > On Fri, 2003-10-03 at 23:39, Sunil Joshi wrote:
> > > All:
> > > Elsewhere Martin had described some issues with colors of graphics in
> > > 1.1.0 on Mac version of Scribus.  While that is indeed the case, I have
> > > noticed a different problem.  I am noticing that when I export a
> > > document as pdf, the colors are washed out.  Eg. here is a screen shot
> > >
> > > http://www.suniljoshi.netfirms.com/scribus/picture2.jpg
> > >
> > > of the print preview function of scribus on the left side, and the
> > > acrobat file of the same page on the right side.  The brilliant greens
> > > and yellows have been completely washed out in the pdf file on the
> > > right side.  I wonder if any one else has seen this issue.
> > >
> > > -Sunil
> > >
> >
> > This can be where you are using "printer" as a destination in exporting
> > a PDF and then judging on screen in Acrobat Reader. Using "printer" as a
> > destination will convert all RGB colors to CMYK upon export.
> >
> > Why? Acrobat Reader - even on Linux has does some color management
> > adjustments to PDF's which have CMYK colors, which is probably the case
> > here.
> >
> > The only time this is not true is if you have embedded or "tagged" the
> > PDF with ICC profiles. In this case Acrobat will honor the tag and
> > adjust accordingly, usually resulting in a much more accurate preview.
> >
> > Both Franz and I have observed this with both Scribus files. I have
> > observed the same with PDF's which I have created in Indesign2 which I
> > fully enabled CMS throughout the process from PS6 and Illy > ID2 >
> > exported PDF. These PDF's are created on pro-level DTP gear which is
> > hardware profiled and calibrated - thus screen to print match with
> > correct settings is dead on. Yet, I still see the same "muting" of
> > colors in both Acrobat and Acrobat Reader.
> >
> > The result is untagged CMYK will appear muted when viewed in Acro
> > Reader. GS View and other viewers will reconvert to RGB and give a false
> > impression.
> >
> > Note - this is important, the preview in Scribus is an RGB PNG generated
> > from raw postscript via Ghostscript. Now, I think the print previewer is
> > excellent, especially as it is derived from real postscript output and
> > no other DTP app has this, it cannot be trusted 100% for judging colors,
> > especially, judging from your screen caps, that you are pushing the edge
> > of CMYK gamut.
> >
> > Now if you are viewing this in full Acrobat, it could be color
> > management is disabled or set with the wrong profiles.
> >
> > Now that is the theory and mechanics of CMS...
> >
> > Observations/Questions:
> >
> > In your case, are you creating the colors in CMYK from the start ?
> >
> > Have you created any kind of profile for your monitor using the
> > ColorSync wizard ? Without a color profile of any kind - all bets are
> > off for judging color based on the screen preview.
> >
> > If these labels are intended for commercial printing, get the Adobe
> > profiles linked in the docs and use US SWOP on uncoated stock as a
> > starting point as your CMYK profile. That is a safe starting point.
> >
> > If you intend to print these to an ink jet, keep your colors in sRGB and
> > export with "screen' as a destination. This is because most ink jet
> > printers although CMYK devices, the driver expects to see RGB colors and
> > will do its own internal conversion.
> >
> > The kinds of deep blue and green highlights which are visible on screen
> > are often hard to reproduce with CMYK. This is called gamut compression,
> > where the dynamic range of RGB is higher than CMYK.
> >
> > Welcome to the sometimes murky world of color management.
> >
> > Now the other side of this is when Scribus has good profiles to work
> > with, the color matching is remarkably good. I created some PDF's of the
> > Scribus logo with lcms 1.11 and the screen to print is as close as I
> > would get from Indesign 2. So yes, the color management does work
> > properly.
> >
> > Feel free to send me files for testing/comments.
> >
> > Regards,
> > Peter
> >
> >
> 
> 
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