Re: G7 press calibration, best press conditions or average?
Re: G7 press calibration, best press conditions or average?
- Subject: Re: G7 press calibration, best press conditions or average?
- From: email@hidden
- Date: Mon, 03 Nov 2008 23:25:28 +1100
Brian, Rick, Rick, Mike, Roger and anybody else I can't fit in,
I find this discussion very interesting as it raises many 'debatable' points. As a teacher of Prepress
I face a daily struggle getting relatively 'simple' concepts across to people that are involved in the
printing and prepress industry. Some of which appear below. When I found a pool of experts debating
them I thought sharing my perspective might contribute something to this discussion.
Let's start with calibration. I tell my students that the purpose of calibration is to get a device into a
predictable and consistent state (which doesn't HAVE to be linear). This might be a digital printer,
imagesetter, platesetter, monitor... This must take place BEFORE profiling: a process of capturing a
description of the tone and colour characteristics of a device AT A SPECIFIC POINT IN TIME.
The same applies to offset printing presses which are renown for their erratic behaviour over time. As
others have pointed out there are many variables in this process and they have not traditionally been
subjected to the same degree of quality control/scrutiny that occurs in other industries. Ink, paper,
press and (unfortunately) press operator, not to mention temperature and humidity.
As a result variations in the printied product WILL occure even throughout a single run. Other
factors such as age of the press and the quality of maintenance will aslo have an impact. It is
unrealistic then to expect a single profile of the printing press to tell you much about what might come
off the production line. When it comes to making a profile of a printing press the first question that
should be asked is "What will the profile be used for?"
Some of the practitioners in this field seem to think that the purpose of a press profile is to capture
the press in an IDEAL state: when the press has just been serviced and all the variables are bolted
down. But how REALISTIC is this profile? When you consider that (in an ideal world) this profile will be
used by Graphic Designers (shock - horror!) as well as Prepress operators to predcit how their jobs are
going to turn out there is a very real danger that they will be severely disappointed. Press profiles
are not just for press operators. As Brian pointed out, the press is just one part of the production
process.
This is the point of averaging profiles: to get a more 'realistic' picture of the capabilities of a press
through the print run. An averaged profile will, by necessity, exhibit a colour space that
is 'compromised' yet more readily achievable ON AVERAGE. This means that, when the designers and
prepress use it to predict the result during soft and/or hard proofing they will see something that is
achievable and realistic, not idealistic. In other words, an accurate prediction of the end result. This, I
thought, was the whole point of a colour management SYSTEM of which the press is one, not necessarily
small, part.
You can even make an averaged profile across different printing presses to allow for the variation that
might occur as a result of the demands of production schedules where the press targetted for the job
is changed at the last minute. Of course, if that press's characterisitics are significantly different the
profile will be compromised again. It allows for more versatility in production management although the
quality will be compromised. As long as it's within tolerance it's OK. Life is full of trade-offs. Especially on
the production line.
This is the whole point of standards based printing. Instead of targtetting a particular printing press,
you target a particular colour space: one that is achievable by the large majority of printing presses.
This is, I would think, is why the tolerances in the standard are, at this stage, fairly... accommodating.
The savings in productivity by 'simply' controlling the device through monitoring of the very well-known
list of varibales, so that it's behaviour is always within a prescribed set of parameters (as described in
the standard) is (or should be) the job of the press operators and those charged with their supervision.
To those that think this is demeaning the role of the press operator as a 'button pusher' I ask "If I had
to get my car repaired and the repairer said "WHICH spray painter would you like to paint your
car? If you use George it will be a different shade than if you use Fred." I think I would look for another
car repairer.
Mark Stegman
Teacher
Graphic Prepress
Sydney Institute
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