Re: Posterisation in a Press Profile + Standards
Re: Posterisation in a Press Profile + Standards
- Subject: Re: Posterisation in a Press Profile + Standards
- From: email@hidden
- Date: Wed, 07 Oct 2009 09:02:25 +1100
Paul,
(Apologies to Mike - I will be tedious. No risk.)
Paul, your statement "A press cannot be characterized or profiled. Only printing conditions." needs to be addressed. Steve Upton has already responded. Hopefully, I can add something useful.
I agree that a printing press is a comparatively 'wild' device compared to say an inkjet printer but your blanket statement is also a bit 'wild'.
A recent topic on this forum was press "calibration" which is directly related to what you are saying. Some had trouble getting their heads around the concept that a press could be 'calibrated' just like
any other device because of its 'wild' behaviour. Calibration seeks to achieve a predictable and consistent state. A consistent performance to a set of predetermined criteria - the printing conditions. As
we all agree, it is the essence of process control. Traditionally we have done this by measuring solid ink density, dot gain, hue error and grey balance as a minimum set of indicators to monitor and
control. These parameters were/are dependent on the ink, paper, press and process. You CAN'T separate them.
The fact that there may/will be variation has always been a fact of life and so we have built 'tolerances' into the acceptable range of variation. These tolerances are incorporated into the very
standards you refer to. The main difference is that they are no longer defined solely in terms of these 'traditional' parameters but include more 'sophisticated' measurements e.g Lab, Delta E, TVI..
In other words, just because a device will vary does NOT mean you can't profile it. If you can calibrate it, you can profile it.
Calibration, process control and profiling are all tied by the same umbilical cord. The 'traditional' parameters are NOT redundant in a workflow based on ICC profiling. In fact, they underwrite any
characterisation and subsequent profile that is generated. If you can't maintain these traditional parameters of process control then indeed, you can't generate a valid profile. However, if you can
maintain process control so that measurements fall within the range of acceptable parameters (tolerances) then you can generate a valid profile. This profile accounts for the variation by targeting a
colour space that is mostly achievable as long as the pre-defined ink, paper, press and process are used. Standards are NOT based on 'ideal' printing conditions. They are based on achievable ones.
To base them on the optimum performance capabilities of the latest printing press would render them as useful as a formula 1 racing car in your garage.
This is a point that seems to be lost on many. Standards based profiles, generated from an acceptable range of characterisation data, are NOT about perfection. They are about achievable consistency
in mass production market. You can achieve results that are, in terms of colour gamut, saturation and dynamic range, 'better' than the standard. However, this limits their 'reproducibility' across a
range of printing presses and defeats the purpose of the standard. There is nothing stopping you from differentiating yourself in the market by achieving such high quality results. However, if your
client is looking for a result that is achievable outside, as well as inside, your production environment you are putting yourself in a niche market, not a mass one.
Back to profiling. In a standards-based print production environment the profiling process is simply turned on its head. That is, instead of using individual press profiles you streamline the production
process (and the colour management process) by getting the presses to target one profile - the standards based one. The principal is simple although the implementation is often fraught with traps and
profile generation seem to be one of them.
To turn this process on its head again we have learned to 'compensate' for the individual characteristics of a press by simply adjusting the tone curve (TVI) at the platemaking stage. In other words,
we compensate for the behaviour of the individual press by adjusting\editing the profile. The adjustment produces a result that is tailored to the peculiarities of the press but still within the parameters
of the standard so it's OK. It's a 'different' profile but it's still within the range of the specifications in the standard. As long as you monitor the output regularly and consistently you should minimise
your problems. It is as much a risk management process as a quality assurance one (if there is a difference).
However, to say that you have to use standards based profiles because you can't make acceptable press profiles is just not right. If you can't make an acceptable press profile then it is unlikely that
you will be able to get the press to perform within the process control tolerances of the standard. Perhaps you meant "If you can't generate a profile that falls within the acceptable range of the
standard...".
The bottom line is that, if you want consistent quality, the press has to perform consistently. To do this, it has to be calibrated - monitored and controlled. Profiling 'just' describes the characteristics of
the press and helps you predict the outcome in order to make allowances for it. Just like we've always done?!.
Mark (the tedious one).
>
> This is indeed very true...
>
> A press cannot be characterized or profiled. Only printing conditions
> can be
> characterized/profiled. (A press offers uncountable conditions)
> So why not target a standard printing condition? Good profiles are
> freely
> available. (Manually tuned and tested and still tested and
> retuned...).
> Custom printing conditions should only be used in closed-loop
> situations
> where ideally only one party is controlling the process.
> Process control is the key.
>
> Paul
>
>
> At Fri, 2 Oct 2009 12:47:25 -0700 Steve Upton <email@hidden>
> wrote:
>
> > At 1:00 PM +0200 10/2/09, Paul Foerts wrote:
> >>
> >> This is indeed very true...
> >>
> >> A press cannot be characterized or profiled.
> >
> > unless we are talking about different things, I'm going to have to
> disagree.
>
> When a press is used as a color correction tool (aka profile editor)
> in
> pursuit of pleasing color, different printing conditions can occur on
> one
> sheet...
>
> >> Only printing conditions can be
> >> characterized/profiled.
> >
> > Printing conditions are specifications written on a piece of paper
> than
> > prepress and a press operator follow in order to print. The prints
> created by
> > said press operator can be measured and profiles can be built. So I
> think we
> > must be talking about different things here.
>
> Yes, terminology in printing is rather fuzzy.
> In my view, a printing condition is the result of a press setup.
> Any variation of process parameters (prepress and paper included)
> results in
> another "condition" of the press. Targets collect these variations.
> As many targets (profiling charts) printed, as many profiles can be
> built: a
> profile for every (?) printing condition.
> A specification may contain information about the use of a
> standardized or a
> preferred printing condition.
>
> >> (A press offers uncountable conditions)
> >> So why not target a standard printing condition? Good profiles are
> freely
> >> available. (Manually tuned and tested and still tested and
> retuned...).
> >
> > Yes, but those 'standard printing conditions' are data sets that
> were derived
> > from prints obtained from real press runs. Granted for
> characterization data
> > sets like GRACoL, SWOP, FOGRA, etc they have undergone a lot of
> averaging and
> > smoothing but they are still from presses.
>
> Standard printing conditions are derived from an "ideal" printing
> condition.
> Highest precision press, best paper, inksets optimized for max. color
> gamut,
> using standardized screening and platemaking.
> In test runs, technically optimal inkfilm thickness is set.
> Paper type differences and process tolerances make the picture
> complete.
> Characterization data is collected from these runs.
> If the "standard" cannot be met by most of the printers, rejection
> may
> follow :-(
>
> Better presses, better/other inks, changes in platemaking
> standards...
> may ask for "actual" characterization data, a never ending task.
>
> >> Custom printing conditions should only be used in closed-loop
> situations
> >> where ideally only one party is controlling the process.
> >
> >
> >> Process control is the key.
> >
> > well I can't disagree with that!
>
> Thanks!
>
>
> Paul
>
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden