this whole pdf/cmyk discussion has been a nice exercise for me
in getting to "know the activity" as Don Norman calls it.
this is what I digest from all that has been said here:
rule #1: the topic we are talking all the time about here
is not cmyk, tiff or pdf. the topic we are talking about is
mastering for the printing press
everything evolves around that.
2) even though the printing press can be digital, plates is
what it is all about. cmyk is the bleeding obvious way
to set up those plates, but anything can happen (spot, CMKYGO).
3) control over what is on each plate, and then how they combine
is the name of the game. I do not underestimate how much
adjustment is needed for each plate (or multiple plates),
basically the whole monochrome collection of image operations.
4) tiff or pdf? it is just a transport method. it is a strategic
choice what to do first/better/at all.
5) there is the creative work to make the image and there is
the mastering for the printing press. in general these two
jobs randomly alternate during the life cycle of the image file.
one moment there is creative development, the next there
is work on the plates, then back to the creative part, etc.
6) if an image is in cmyk then we are stuffed when it comes
to creative work. lots of operations/plugins will stop
working or only via (implicit) cmyk->(other color model)->cmyk
conversions, which are a no-no.
7) when opening a file in cmyk format, it has obviously been
mastered for a printing press. either this mastering needs
corrections, or this image is an 'found image' that goes
into another creative work. the latter is better done in
rgb (see 6).
8) trapping is an example of explicit printing press support.
9) it is necessary to set the same point on all plates to an
exact ink value (think of setting a hard cmyk value for a
block of text or selection of pixels).
after writing the above I have reread for the third time all
the emails in the thread. AFAIK all the input in the thread
is captured in the above observations.
my conclusions from this:
1) all creative work in GIMP is in rgb.
2) when it is one of those times (plural) to work on the
printing press mastering of this file, then pull the
"press projection" over the image window. now you can see the
plates (similar to layers) and work on each or combinations.
3) the set-up of the press projection plates is of course
the separation set-up (with printing press profile) and
can be freely defined from the composite or individual
layers of the image file (channel mixing on steroids).
standard cmyk type of separations will be the bleeding
obvious defaults to choose from. CMKYGO can easily be
also a default.
4) flip the press projection up again and continue to work
on the creative part. flip the press projection down
again and the plates are updated from the image changes.
with previous plate modifications applied on top.
5) the press projection set-up and all modifications made
to the plates on the press projection are also saved in
the GIMP file.
5) when it is time to send the printing press master then
from the press projection it can be exported to a few
suitable formats (tiff, pdf, ...).
6) importing a cmyk file? there should be a choice to either
shove this straight into a press projection to do some
mastering corrections, or to convert to rgb to be part
of a new work of art.
founder + principal interaction architect
man + machine interface works
http://mmiworks.net/blog : on interaction architecture
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