On Mon, 23 Mar 2009, Sven Neumann wrote:
> On Mon, 2009-03-23 at 17:51 -0400, Andrew A. Gill wrote:
>> I do work in the printing industry, and I can tell you that
>> output is still CMYK, and will remain CMYK for at least the next
>> few years.
> Output, yes, of course. But where in this process do you actually edit
> an image in CMYK? I don't mean converting it to CMYK to get it printed.
> I mean actual editing after the conversion. Could you give us some
> examples of where that is needed?
Like I said, I mainly work with vectors and spot jobs, but I
have, in the past, had to deal with some of these issues. Take
the following image, for example:
To properly print this image, it should be trapped--that is,
either the red plate or the black plate should be altered so that
the red and black overlap. That way, a slight misregistration
won't result in a white gap along the border. Trapping is
usually pretty small, around .25 pt, but here's an exaggerated
example of what will happen if you don't trap and the plates are
Some trapping can be done in vector programs and page layout
programs, but images with non-geometric edges like the one above
cannot. I would have to do it in GIMP, but I cannot do it in
GIMP, because that would require having some of the pixels at
100% red and whatever shade of black it is at that point, and
GIMP cannot do that because it does not have CMYK support.
Likewise rich black. In cases where you are printing black on a
multicolored border, it's useful to print in rich black, usually
60%C, 100%K. This makes the effects of trapping less noticeable.
You can find an example of rich black here:
Again, it is not possible to do this in GIMP without CMYK
Also, color correction. If I print a proof and it turns out that
it is too cyan, I cannot simply turn up the red, because that
will also adversely affect both the cyan and magenta plates.
And finally, I agree with Sven that I don't know why anyone would
want to have multipage PDF output for GIMP. I'd much rather see
built-in DjVu support.
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