[Openicc] Fwd: linearisation targets, Argyll, G7

[edmund ronald]

---------- Forwarded message ----------
From: edmund ronald <edmundronald at gmail.com>
Date: Jan 24, 2008 1:02 PM
Subject: Re: [Openicc] linearisation targets, Argyll, G7
To: homann at colormanagement.de


I think this reasoning is correct, but does not apply in the context
of inkjet printers:

The user model may be RGB or CMYK, but the printer runs natively in
CcMmYKk space or something like that. The purpose of the basic
linearization is to establish what the abilities of the individual
ink-guns are - eg before even the crossover point between K and k gets
defined. Thus, measuring the ink-flow out of each *ink-gun* is what a
linearisation tool should allow the user to do first, eg. with a step
chart for k and a different one for K, and one for both C and c. The
values here will assist the user in setting up; heuristically, the ink
curves by means of an interactive tool which needs to be constructed.

Edmund

On Jan 24, 2008 11:44 AM, Jan-Peter Homann <homann at colormanagement.de> wrote:
> Hello Graeme, hello list
> I don´t think, that a linearization for a shared visual appearance is
> only useful for set up CMYK printing presses.
> Especially in in the Inkjet area, we have a lot different printers and
> media. If the the linearization targets for all of this printers / ink /
> paper combination lead to to similar gradation and gray balance,
> workflows with standard profiles will be much more stable and predictable-
>
>

> For the CMY-scale a scale with different near neutral CMY patches is
> printed and measured or visually compared to reference print samples.
> The linearization goal could e.g. be, that C50 M40 Y40 should lead to
> L*57 a*0 and b*-1.
> If e.g. the CMY patch C30 M25 Y30 leads to L*57 a*0 and b*-1, the
> correction-curve for linearization should correct C50->30 M40->25 and
> Y40->30.
>
> As the eye is very sensible for the neutrals, a re-linearization /
> calibration to a good gray balance and gradation will do the job, most
> users expect for a good printer-setup.
>
> Both the basic linearization and also the re-linearization/calibration
> could be done either by measurements or by visual comparisons with
> reference print samples. As I described in my last e-mail.
>