Digital BW, The Print

From: "Tyler Boley" <tyler@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, June 07, 2003 4:41 PM
Subject: [Digital BW] For Ernst was Re: IJC on w2k ...


> Ernst, I'm sorry this went right by me at first
>
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Ernst
Dinkla" <
> E.Dinkla@c...> wrote:
> ...
> > use that setup for Ultratone VM inks. One of the decisions in
> > curve control was whether the greys should be used to their
full
> > 100 % in each curve separation or let the next one take it
over
> > at 90 %. I think much of the softness, lack of small detail
is a
> > result of the right setting in that part of the curves and
> > related to the dithering quality of the driver. If the
dithering
> > quality is excellent then you better end the curve early and
let
> > the next grey take it partly over with low percentage ink and
the
> > good dithering. The 90-100 % dithering is always harder to
> > control than any dithering in the 0-30 % part.
>
> The driver I use seems jumpier in the 90-100% areas, but I was
unaware
> possible of dithering problems. Also, with some inks and
papers, mottle
> and
> bleeding will result with a RIP that can pour ink down, that
can
> certainly effect resolution.

Paul once wrote that so many are looking for dotless prints but
the chance that detail is lost by stretching the light inks too
much is always around the corner. That's more of a problem with
RIPs and Gimp-print derivatives than with the Epson driver as the
last is frugal with ink.

> I'm not familiar with the inkset, but I'll try to follow. The
only part
> I don't get is how you remain somewhat linear overall when
introducing
> the toner. Do
> you have to go back to the CcYK curves and rework them to a
lower gamma
> to make up for the addition of a given amount the toner? Mm
sounds easy
> enough, it's just one channel. More or less M out of PS will
take care
> of that since the Mm is linearized in the RIP right? But I
don't know
> how you can
> have overall (but still linear) density control of CcYK. The
blending
> options in OPM/IJC, the new R9 RIP, and the new Cone seem
attractive in
> this regard.

The Wasatch SoftRip has a set of calibration curves for the Epson
9000 and on top of the calibration curves a set of correction
curves, both set of curves are Cc, Mm, Y, K, so 4 calibration
curves for 6 inks + 4 correction curves for 6 inks. There's a
total correction curve as well, inklimit and lighter slider
settings are expressed in that curve but it can be manupilated in
the curve itself too. There's also a separate setting for the
transfer point between C and c + M and m, default 50 % at 100 %
max inklimit but that can be changed, Wasatch advises to keep it
at half the inklimit setting in colour printing.

The toner channel(s) Mm are linearised from the start, one
reading and one calibration curve for both so about 9 nodes per
channel. So far I have made a neutral set only and the correction
curve has been straight from 0-100.  It is slightly warmer than
Paul's neutrality. I could linearise the other channels first too
and build on that the correction (separation) curves but I
thought if I do the correction (separation) curves first then I
can measure the Y,mM,K total ink greyscale target in one go and
linearise the Y,mM,K channels with a copy for each. It only
linearises per channel the part of the greyramp that is actually
active in that channel. It isn't entirely correct as the total
linearisation can't distinguish between the contribution of two
greys at the two overlaps Y-c and C-K (the one between C and c is
taken care of in the Wasatch system) but by adjusting the
separation curves till the last linearisation curve is almost
straight there can't be much wrong in this approach. But I had
not thought of the fact that by using a single channel curve
(target) of 18 nodes and stretching that over the entire 4
channels Y,c,C,K they become too rough for the task. It might be
better if it is done with linearisations per channel first but
the best would be a more samples, more nodes, total
linearisation.
Wasatch isn't responding so far but I keep it going.

When the toner is linearised and the total greyscale without
toner too then the two together are linear as well. The subtler
warmer colder settings have to be done on the total correction
curve and the toner correction curve. Opposed Gamma shifts. For
the warmest set the toner can be entirely removed I guess, there
is enough grey ink left in the "60 % lighter curve" that is
already used in the neutral curve to keep the density of the
cooler and warmer sets alike.

>
> > is on another XP system and I throw
> > a simple straight CMYK 0-100% conversion of a greyscale file
on
> > it that is made with a PS action. Yesterday evening I got a
small
> > application that a friend has made which converts a 16 bit
> > greyscale tiff into a plain 16 bit CMYK tiff (it has to be
> > changed to LZW compression in default as that will make the
files
> > much smaller).
>
> This is interesting. So you send it a full on 400% CMYK file
and do all
> of the partitioning in the RIP?

Correct. The warmer and colder settings are saved in the RIP and
can even be connected to hot folders so the 4 printers the RIP
can drive at the same time can be multiplied into several virtual
printers per real hardware printer.

> > In the process I made a linearisation target that is
dedicated to
> > the Ultratone VM inks driven by the Wasatch. I have used
> > Spectrocam readings as my Gretag densitometer is not reliable
at
> > higher Dmax anymore and the SoftRip is compatible with the
> > Spectrocam.
>
> I still use my Spectrocam for everything. One day it will
explode and
> that will be that.  I've not seen the problems others have
reported,
> though I'm not going
> for, or measuring Dmax's higher than pigment K on art papers.

Being used to the Dmax of Generations Enhanced I was disappointed
with the Ultratone Dmax with the Epson driver. Paul's curves are
excellent but he can't get past that limitation in the Epson
driver. On German Etching it must now be near the 2.00.

> > Another approach that is possible is the use of Paul's VM
curves
> > cnverted to RGB profiles and the Wasatch paper-ink settings
> > adapted to the Epson driver. The Wasatch SoftRip can be made
into
> > an RGB device though it is CMYK in default. That would allow
> > printing straight from a greyscale but I find it less
transparent
> > and I guess that I can get more in this way.
>
> That's an interesting idea too. I wonder how well it would
mimic the
> Epson driver. But you're right, it's more convoluted and you
have less
> ultimate control.
>
> Qimage sounds very interesting, and I wish there was a Mac
version. Are
> you saying it limits black D?

It uses the Epson driver so it can't do more than that.

> That is the current problem with Gimp-print. I'm told the next
release
> will allow much higher density, I find it too low right now.
Roy's work
> with it is really
> great and still progressing, my testing with it is way behind.
They
> need to get that density up though, for it to compete with
other
> options.

If I can't get it done with the Wasatch I will go Roy's route on
Linux.

Ernst