RE: Posterisation in a Press Profile + Standards
RE: Posterisation in a Press Profile + Standards
- Subject: RE: Posterisation in a Press Profile + Standards
- From: Roger <email@hidden>
- Date: Tue, 06 Oct 2009 21:00:32 -0400
Hey Mark,
I enjoyed reading your post. I'll put you in the "non-tedious" camp ;-)
I remember first reading about press calibration a few years ago, and I can
distinctly remember how that concept was just an anathema to me back then.
Today, it's become a mantra. Not a panacea but a way of living -- peace
brother. Why can't a printing press be treated like any other device? It
seems to be an idea that took a long time to take shape among printers in
North America, everyone was printing to their own house standards trying to
outdo the other guy.
Having said that, it worth pushing the idea of calibration a little further.
To me, there is "calibration" and there is "calibration". Duh! My hypothesis
is that a press "calibration" isn't an absolute in itself. On a given
substrate, using a given set of ink, at a given ink/water balance, at a
given press speed, using a given set of blankets, using a given set of plate
curving, it seems to me that various ink coverages, caused by various kinds
of imagery (low, normal or high key), require different volumes of ink
distribution, in order to match a certain proof standard. So, in a sense, it
would seem incomplete, in my view, to talk about press calibration without
also referring to the accompanying "ink load": at what ink level was a given
press sheet/calibration obtained, I think is the interesting question. It
may sound crazy but I run into this situation every day. To print "normal
key" images, the press draws ink volume X from the ink train. If we were to
stop the press abruptly, to measure the amount of ink on the rollers, we'd
probably find a certain thickness, which can be measured. But to print "high
key' images, the press does not need to draw as much ink from the ink train,
thereby changing, in my opinion, it's ink response (I don't know how to
better word this). This differential ink load, IMO, is the reason why a
given calibration cannot be universal or absolute, in its capacity to bring
a printing system to a "known" state. It is my belief that calibration is
imagery-dependent. Can a printer develop different calibrations for the
broader categories of printing? That would be pushing. But it would be
interested to experiment.
Have you ever ran into these situations yourself? Does the phenomena I
describe sound rubbish to you?
Haven't found much in the literature on this subject... Yet, it is a real
problem.
Best / Roger
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