Re: Colorsync-users Digest, Vol 5, Issue 388
Re: Colorsync-users Digest, Vol 5, Issue 388
- Subject: Re: Colorsync-users Digest, Vol 5, Issue 388
- From: email@hidden
- Date: Tue, 04 Nov 2008 08:30:25 +1100
Roger,
Thanks for your thoughts and encouragement. Unfortuneately, they seem to be lost on others.
Mark
> ------------------------------
>
> Message: 11
> Date: Mon, 03 Nov 2008 09:10:11 -0500
> From: Roger Breton <email@hidden>
> Subject: RE: G7 press calibration, best press conditions or average?
> To: email@hidden, email@hidden
> Message-ID: <002d01c93dbd$e2a3aae0$a7eb00a0$@ca>
> Content-Type: text/plain; charset=us-ascii
>
> Mark,
>
> Thank's for your two cents. You raised a number of interesting
> points.
>
> > 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).
>
> My thoughts exactly.
>
> > 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.
>
> Interesting point. In the GMG RIP, it is key that calibration be
> done
> *prior* to profiling. Otherwise, when re-calibrating every other
> week, let's
> say, the profile would be rendered useless because it would no
> longer
> describe the printer in a known, calibrated condition. Fantastic
> point! I
> use GMG as an example but I'm sure everybody get the idea.
>
> > 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.
>
> Yes, they have not. But I suspect they will as color management
> gradually
> tightens its control on every variable involved in the process. But
> the
> pressroom is a tough environment to change. It seems only when
> clients
> complaint and threaten to take their business elsewhere that change
> can
> finally be brought about.
>
> > 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?"
>
> True. It's ludicrous to believe that one press profile will capture
> the
> essence of the press behavior in its many moods and temper but that's
> what
> we have to hold it against, nevertheless.
>
> > 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.
>
> That part of the process is not easy to deal with.
>
> > 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.
>
> Right. The keyword here is realistic. But it has to be coupled with
> customers's expectations. Some, as we know, are not realistic. Others
> demand
> the utmost quality and are willing to pay for it. I think everything
> is
> possible provided adequate resources are thrown at the problem in the
> form
> of money and time. Heck! Look at what Bill Atkinson has done with
> its
> Stones. We can debate all night long about the true quality of VanFu
> inks
> but, in the end, I think Bill got away with some of the best quality
> one can
> ever get from an offset sheetfed press. Never mind Hexachrome or
> stochastic,
> just on the process control and repeatability of the whole system. As
> you
> said, Mark, we're all looking for predictability. That's the holy
> grail of
> this exercice.
>
> > 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.
>
> Wow! I'm steeling the words off your mouth...
>
> > 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.
>
> For those who insist on making custom press profiles as opposed to
> using
> ISO-type or CGATS-type synthetic datasets, such as GRACoL2006_X, I
> see the
> need for better anylytical tools. It's one thing to aggregate a bunch
> of
> measurement files, throw them in MeasureTool or PatchTool to average
> them,
> but I see a missing link in the form of advanced statistical tools
> that
> would allow analyzing a bunch of measurements files to extract
> meaningful
> information about the underlying process. I have not see anyone doing
> this
> in a commercial system, maybe that's too much to ask?
>
> > 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.
>
> Yes.
>
> > 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.
>
> I'm with you 100%.
>
> > 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.
>
> Love your reasoning ;-)
>
> You should post more often!
>
> > Mark Stegman
> > Teacher
> > Graphic Prepress
> > Sydney Institute
>
> Roger
>
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