[softwarelist] Re: colour corrections
- From: Mike Williams <akalat@xxxxxxxxxxx>
- To: <davidpilling@xxxxxxxxxxxxx>
- Date: Thu, 30 Nov 2006 13:38:15 +0000
On 30/11/06 1:06 pm, "Martin Wuerthner" <public@xxxxxxxxxxxxxxx> wrote:
> In message <e54be88d4e.arnold@arnold.>
> Arnold van der Heijden <info@xxxxxxxxx> wrote:
>
>> When I use -for example- 100% magenta in Ovation, print this
>> postcript, the file never gives, depending on the jobobtion in
>> Distiller, 100% magenta in pdf.
>
> This is not surprising. The RISC OS printer driver is strictly
> RGB-only, so what ends up in the PostScript file is always an RGB
> colour. This is not OP's fault - there simply is no way to tell the
> printer driver that a CMYK colour is desired. So, in the case of the
> standard 100% Magenta CMYK colour definition, the colour setting in
> the PostScript file reads:
> 255 0 255 C
> which sets 100% Red, 0% Green, 100% Blue, which is the naive
> conversion of 100% Magenta from CMYK to RGB. It is highly unlikely
> that any printing pipeline will render that as plain 100% Magenta.
>
> By the way: It would be almost trivial to enhance the PostScript
> printer driver to allow applications to set CMYK colours. This will
> probably be done as part of the PostScript 3 driver project. Adding
> support for that to OvationPro should be very easy.
>
> As a further aside: OvationPro does have special code to bypass the
> printer driver in order to print CMYK bitmaps to PostScript correctly.
> This has a long tradition: Impression did it already, and ArtWorks
> does it (I added that for ArtWorks 2.4).
>
>> I tried all kind of settings, different joboptions, colour
>> correction turned on or off. But I can't get 100% magenta
>> as 100% magenta in pdf. It does not matter Ovation Risc Os or
>> for Windows.
>
> The only way to get CMYK colour definitions for shapes and text into a
> PDF file under RISC OS is to use a program that generates PDF files
> directly instead of going through the PostScript printer driver, which
> flattens everything to RGB. If you export as PDF from ArtWorks 2 you
> get all your original CMYK colours in the PDF file.
>
> Martin
It may not be what you want, but a possible solution is to deal with each
CMYK channel in turn, so that all channels other than your choice are
switched off. Make sure that you configure the Postscript driver so that
colour output is disabled. Then create your postscript file, which will in
effect be in monochrome, but can of course be printed in whichever CMYK (or
other) colour you specify. Because all 4 separations are created digitally
they should line up accurately for printing purposes.
I have used this approach for getting printed work originated in Impression
to be printed black and one Pantone colour, specifying the spot colour to
be, say, cyan defined as a CMYK colour. This enables tints and gradations
(some from Artworks) to be separated correctly.
I think you will find that 100% Magenta is then converted into 100% black.
Of course, if you are outputting direct to a desktop printing device then
this will not work, but it does get round the problem, if crucial, for work
on a litho press.
I have also found that the company I use for digital printing (on an Indigo
press) can now cope with RGB colour, so I simply create an RGB composite
PostScript file converted to PDF (using Distiller on a Mac in my case) and
it prints very well.
Mike Williams
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