Re: Inkjet Proofer Separation Parameters (cookbook ABC...)
Re: Inkjet Proofer Separation Parameters (cookbook ABC...)
- Subject: Re: Inkjet Proofer Separation Parameters (cookbook ABC...)
- From: Henrik Holmegaard <email@hidden>
- Date: Wed, 29 May 2002 09:47:13 +0200
Jack Kelly Clark <email@hidden> wrote:
>
I've found the Black Start parameter to be very confusing both
>
for me (especially me) and many of the prepress managers I deal with.
Each profiling application has a different black replacement technology just
as it has a different gamut mapping technology.
Black start is a control that lets you determine when black replacement
starts as you move from the highlights into the shadows. By and large you
want a black start that keeps black dots out of highlights and midtones on
inkjets. A black start of 40% is default in both ProfileMaker and Eye-One
Match.
Because the elementary spot size of an inkjet is larger than the elementary
spot size of an offset press, you want to keep optically dark inks out of
highlights and midtones.
This is also why inkjets split dark Cyan and dark Magenta into dark Cyand
and light Cyan plus dark Magenta and light Magenta in printer firmware,
whereas black is left to the ICC profile (or built-in CRD if you enable
PostScript color management).
>
I am profiling a commercial printer's HP5000PS inkjet proofer, which
>
they have carefully calibrated to their presses.
>
should I use the numbers I got from the prepress manager
>
(UCR,Total Ink 310%, Maximum Black 98%, and Black Start ?)
The Proof-printing cookbook gives a complete Adobe settings tutorial for
this printer with it's hardware Adobe PS3 RIP and built-in ink limiting,
which IMO is the reference for a simple and straight proofing workflow. It's
been ready in version 16 for months, but for whatever reason it's not been
released along with the inkjet profiling ABC it also contains. There was
some movement a week or so ago, but I do not control these things: There is
a broad prereading group and a narrow release group and copy has to clear
both instances on a consensus basis.
In any case, you don't want to hardware calibrate the PostScript inkjet to
the press any more than you want to hardware calibrate a monitor to a paper
with the Knoll gamma tool.
The art of separation is to keep ink levels as high as possible without
causing contiguity problems (: loss of detail through over-inking). If you
cut back ink too far, you shrink the gamut.
The ink limiting should happen in the RIP *before* you print the test chart.
If the test chart is over-inked or under-inked, the gamut is already
impacted in the measurements you capture.
On the 5000PS there is built-in ink limiting. Just choose the paper setting
that comes closest to the third party paper you are using, typically
'Proofing Satin' works well. Secondly, set the RIP to calibration and
finally print your test chart. In your print profiling software, set the ink
limit to 400% because you want the profile to manage color and black, but
not ink limiting.
On an offset press, though you calibrate the process prior to running the
test chart and might in principle set the profile to 400%, you don't want to
do this for many reasons. A press layers fatty inks on top of the paper or
economic high speed printing, but inkjet inks penetrate the paper and
require drying. For production reasons you normally want a lower ink limit
on the press than it is maybe capable of, you want to avoid color shifts by
using black instead of CMY throughout the color space, and also to save on
expensive CMY inks.
So your settings should be: Preset Inkjet 400%, either Paper Gray or
Preserve Gray, LOGO Classic (in PM4) and Large as profile size in order to
obtain the maximum precision from your proofing profile. Note that your
profile for the press should also have maximum precision for the A2B
simulation direction.
Hope this helps.
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