Re: New SNAP Standard (GCR instead of UCR)
Re: New SNAP Standard (GCR instead of UCR)
- Subject: Re: New SNAP Standard (GCR instead of UCR)
- From: "eric@poem" <email@hidden>
- Date: Mon, 24 Aug 2009 11:33:03 +0100
On 23 Aug 2009, at 14:13, Roger wrote:
Eric,
Assuming newspaper conditions are similar, this profile works very
well in my experience. The caveat, as has been mentioned on this list
before, in order to get the correct TAC value of 240%, RGB to CMYK
conversions must be executed using perceptual intent with Black Point
Compensation switched off. Otherwise you get a lower value around
212%.
That is still a mystery to me. And the appearance of the color in
Photoshop,
once separated, too. I still have not gotten over that. Almost as
bad as
Egypt's pyramids...
I always have soft proofing enabled, with paper simulation off when
processing images because of the slight brightening that happens due
to the conversion.
I agree the images can sometimes look a little strange, but the full
soft simulation with paper-white invoked gives that much needed
reality check!
In passing, I have found that in this age of digital photography,
when
processing images for newspapers it is always advisable to open up
the
shadow range.
Ah! Very good advice, Eric. Especially with newsprint. Some people
have a
tendency of trusting their monitors too much. I know the resulted
"dumb
down" images may look washed out on the screen but, on press, the
details
will be there, well preserved. One job I just seen ran on newsprint
last
week, had all mechanical black graphics made up of 400% ink! Someone
instructed the poor designer to make all black graphic elements (not
text --
thank god!), like the background of some dropped white titles, not
"Black"
but "Registration". And the poor printer is blamed because those
elements
turned "red" or "blue" on press. Some clients have too much power on
printers...
I think all print companies nowadays, but especially newsprint, need
to have a PDF preflight and optimisation workflow to overcome this
exact problem. Whilst I feel that the authors of the content should
supply files fit for purpose, it seems crazy to me that anyone would
allow any file anywhere near their press that contained content that
would seriously trip them up.
All digital photography, with the possible exception of
Still life studio, has a tendency to close the shadows down. The
detail is there in the file, and can be seen in the histogram, but is
compressed and giving it a little room to breath does wonders for the
Printed result.
Would you venture to say that this approach has applications too for
Commercial work? On web printing coated paper?
Yes, definitely. With correct processing, the range of the image can
be opened up, without the colour being massively changed, (although
this can be the aim of course). The improvement in the overall
contrast of the image, that is opening the local contrast in the
shadow region, the opening of the midtone, some highlight range
recovery, gives a much more forgiving image on press. This is what I
mean by "room to breathe", especially important on lower quality papers.
The look up tables were loaded into the cabinet on 8 inch floppy
discs!
Wow, 8 inches floppy disks? You guys were true pioneers!
... I am particularly
gratified, and a even a little smug, remembering the resistance, that
GCR is a vital component in standardised printing, and for those that
go further than the levels in the standard profiles, in optimised
printing. The fact that it is possible to greatly reduce ink levels
and still retain colour fidelity and accuracy with modern colour
science is stunning- but the press crews must be aware of the change
of importance when switching from a UCR style skeleton black, to a
full range GCR separation. A traditional black tends to be used and
abused, and the black unit might well be the Cinderella of the press,
but with full GCR it is the Belle of the Ball!
Eric
If you had the choice, would you go medium GCR for all commercial work
today?
The only problem I have with GCR, in general, and you may disagree
with me,
is that, most often, printing presses are a little off (I'm
generous) from
where they should be, in terms of calibration, be it TVI or Gray
behavior.
Most often, for example, the magenta ink is way too saturated in its
a*
component (76 vs 70), or too negative in its b* component (-7 vs -3),
compared to, say, GRACoL or SWOP. Worse, when those same magenta ink
are
screened, say, down to 50%, their b* component can increase
negatively to b*
= -11 (typical, believe me). So, what happens with those skin tones
where
the b* for magenta is built, at separations time, for b*=-4? The
skin looks
overly bluish, and I've seen that, regularly, on paper having b*
close to
zero! That's why, I feel, for many actual work, UCR offers the
advantage of
"more room to manoeuvre" on press than GCR. I don't dispute all the
advantages for GCR, like, in neutrality, for jewelry and silverware
work,
and so on. But, in terms of "helping" the typical press achieve a
satisfactory match to the proof, I see UCR still playing a vital
function.
Not for the right reasons, mind you, but still.
In general yes, but I have had instances where amendments to the GCR
level contained in a standard profile have been applied. This has been
as a consequence of some level of non-conformity to that standard
condition at the printers, generally to do with mis-applied plate
compensation curves. We are still some way from some of our print
collegues "getting" the significance of plate curves and TVI
conformance in my view.
So for instance, whilst the width of the GCR level has been
maintained, the start point has been raised, so that the highlight to
quartertone range is defined in conventional terms, which has help
light fleshtones. Also sometimes a change of screening system helps in
this region by amending the visibility of the rosette pattern caused
by all four colours being present. I am a fan of the euclidian system
as opposed to the ellipitical in this regard, with an open rather than
closed rosette.
I have not experienced this directly, your observations are very
interesting, maybe a difference in the ink set typically used in the
UK/Europe? But I have experienced variations from proof to press. I
think that even in the best proof simulation you can experience
problems on press, not apparent in the proof, due to the fact that
printing is actually a different process in the way that colour is
built up. Especially on lower grade substrates, the dynamics on press
sometimes work at variance to the proof.
I would think that the two examples you have referred to, the 400% TAC
file and the press problem above are compelling reasons to get local
manufacturing processes and procedure into conformance.
It is a fact that no print condition can tolerate very high TACs, so
optimising input files into standard conformance values, changing the
colour numbers should be considered routine. And understanding we
print with "colours" and those "colours" have to be the right
"colours" as expected by the output intent should go a long way to
solving the day to day angst of our printing colleagues...
What do you think?
Roger
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