[Scribus] getting started with colour management

[avox]

jrm wrote:
> 
> It seems to be standard advice, when setting up colour management,
> to set the monitor to high contrast.  When I do this, much of
> the text on my monitor is fuzzier and harder to read.  Is this
> normal?  (This is with the X Window System on an older LCD
> model, an NEC MultiSync LCD 1850E.)
> 

It's more important to get or create an accurate color profile for your
monitor. 
Note that LCD profiles are quite different to raytube monitor profiles. 



> Another thing I've never understood is why, with colour management
> turned off, graphics have been looking quite different in
> Gimp 2.2 as compared with Scribus 1.3.  For example, I have some
> TIFF files with a red that shows very bright in Gimp but
> considerably darker in Scribus.  I'm *guessing* that Gimp and
> Scribus have been implicitly defaulting to quite different
> colour profiles, but I don't even know whether that's a sensible
> way of phrasing it.
> 
> I've got the vague idea that most software assumes the monitor
> profile would be some flavour of sRGB, with *which* flavour
> being application dependent.  
> 

AFAIK sRGB is a standard without flavours. But there's also plain 
RGB (unstandardized), linearized RGB, Adobe RGB and others.



> If I knew what Scribus assumes,
> then I'd know how to choose a "no-op" monitor profile matching
> the default assumption.  The colour management stuff has got me
> pretty confused, so maybe I missed something in the Scribus documentation?
> 


I always like to compare color profiles to metric units. Everyone knows that
"a distance of 40" is meaningless if you dont know if it's 40 km or 40
miles.
But everyone assumes that "rgb color (255, 100, 100)" or "cmyk (1, 0, 0.7,
0.3)" 
has a fixed meaning. It doesn't, unless you specify with what color profile
you 
interpret these numbers. So, (255, 100, 100) in sRGB is a defined color, as
is
(1, 0, 0.7, 0.3) in Euroscale Uncoated.

For color management, you have to provide a profile everywhere you use
colors.
Then the CM system converts the colors from one space to another as needed.
In Scribus you can set a monitor profile; that is used for sending colors to
the screen.
The printer profile is used when generating PS or PDF without embedded
profiles.
The solid color profile is used when you specify a color in Scribus's color
editor.
And the RGB / CMYK image profiles are used when reading image data without
embedded data (but you can also attach profiles to images individually).

So when Scribus shows an image on screen, it uses *two* profiles: the image
profile
which describes the colorspace of the image, and the monitor profile which
describes
the monitors colorspace. Using both, Scribus (that is the lcms library) can
convert the
numbers in the image file to a new set of numbers which will give the same
color on
screen. If any one of those profiles is wrong, the result is usually worse
than if you
disable CM alltogether.

OTOH, if you have images with an embedded color profile, Scribus can forward
that
into the PS / PDF file, and assuming it gets printed on a printer with CM
support, the
colors should be just right. Just on your screen it will look wrong.

/Andreas


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