[scribus] How to assure pure black and not rich black.

[avox]

John Culleton-3 wrote:
> 
> On Friday 26 June 2009 09:08:25 am Gregory Pittman wrote:
>> John Culleton wrote:
>> > I presume this can be done through the correct color profile.
>> > Or perhaps it requires a redefinition of the black color
>> > swatch. Or maybe it is the default.  The manual defines rich
>> > black but does not explain at that point how to get either rich
>> > black or pure black.
>> >
>> > The issue comes up because some process color presses will not
>> > accept a combination of colors which together add up to more
>> > than 240% total density.
>> >
>> > Guidance appreciated.
>>
>> http://wiki.scribus.net/index.php/What_is_Rich_Black%3F
>>
>> Pure black, AFAICT, is defined by CMYK as 100% K, 0% C, M, and Y.
>> There can be a problem in Scribus trying to get pure black as an
>> end result, since and RGB with 0 for each value will probably not
>> result in pure black. We've had a number of submissions to the
>> list where it seems the sender gets obsessed with getting pure
>> black, and consequently gets upset at not achieving it.
>>
>> In the end, I think it should come down to getting the visual
>> color of black you want with the printed product rather than some
>> absolute mathematically pure black.
>>
>> Greg
>>
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> 
> If under preferences one selects the Scribus Open Office CMYK color 
> set then black is pure black.  Just checked it. 
> 
> Apparently some rich blacks may have too high an overall percentage 
> of ink, such as over 270% total, which gives some digital presses 
> heartburn. 
> 
> 

You can define your own CMYK blacks in Scribus; the predefined ones
are just examples. Via Edit -> Colors you can also check the ink coverage
for those colors. I just did that, and the ink coverage ranges between 160%
to 240% for the extra blacks.

The problem arises when colors are translated from another CMYK profile or
RGB
to the printer's CMYK profile. IIRC some profiles make sure not to exceed a
specified ink coverage, but that's not guaranteed. For example, RGB black
will be
mapped to the darkest rich black available by the profile, not pure CMYK
black.

That said it might be nice to have a customizable check for maximum ink
coverage
in the preflight verifier.

/Andreas
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