11:06 p.m.
Hello, all. I'm based in the US, and have
followed the work of the ECI. Being an American,
it is my nature to antagonize Europeans with
provocative notions. So here goes :-)
The latest release of ISO-12647-2 specifies solid
ink levels with colorimetry, and specifies tone
reproduction curves using graphs. These changes
seem good on the surface, but raise new issues.
1. The color of a solid ink depends on the paper,
the ink, and the ink film thickness. When the
color of the paper varies, how does that affect
the intended color of the solid ink?
2. Color is a three dimensional measure, but the
pressman has just one control, ink film
thickness. Generally, it won't be possible to
achieve the exact color specified by adjusting
ink film thickness. The pressman will have to
estimate the best match, based on three varying
quantities. This will be very frustrating for a
pressman.
3. The tone reproduction curves are shown
graphically, but there is no table or formula
that would enable us to enter values into a CtP
system.
4. The tone reproduction curves vary with screen
ruling. Is this really a good idea?
5. The tone reproduction curves are specified
using TVI, which is a density based measurement.
So, while the solids are specified
colorimetrically, other values still rely on
densitometry.
I set up a proofing system using the FOGRA27
characterization data, and found some differences
compared to typical practice in the US. The tone
curves have lower highlight contrast. I imagine
this is due to the past popularity of positive
plates in Europe versus negative plates in the
US. Also, the color balance is a bit cooler. Gray
balance triplets are basically the same in ISO as
here, so I can't explain this difference.
So, could we use ISO 12647-2 in the US?
We need to bring colorimetry into the pressroom,
but with single valued measurements. Tone
reproduction curves could eliminate a great deal
of variation, if used properly. But, TVI is an
outdated concept. We need a better (and simpler)
solution for creating TRCs.
Currently, there is no interest whatsoever in
color-managed workflows in the US. The ideas
behind PDF/X-3 have no following here. Printers
work with CMYK + spot files. The change from film
to CtP has brought with it color anarchy. Each
printer has created their own color standard,
which is based on whatever considerations seem
logical to that firm. It is normal practice for a
printer to make their own proofs of supplied
files, then do color corrections before putting a
job on press. Sometimes clients pay for this,
otherwise the printer eats the cost. This is
incredibly wasteful, but an accepted practice. In
some cases, quality expectations have dropped to
keep costs in check. In many cases, printing has
become a commodity to be bought on price alone.
So, there is an acute need for standards here,
but few comprehend it. This is a fine example of
the "boiled-frog theory." I applaud the Europeans
on their standardization efforts. The Altona test
kit is a great accomplishment. I'd like to see
similar work done in the US.
-Bill
Since the Altona Application Package, the ISO
12647-2 is now known at a much broader front.
Some seminars and workshops are held in Germany
and Austria to educate and emphasize the
pre-print and print people out there, as well as
print buyers, to also show and give guidance how
to work with it on a daily basis.
I would be very interested on some feedback from
other countries than Germany and Austria, how
this standard is adopted. And if someone is not
working with it, my question is: Why? It is not
a DIN-Standard or a Ö-Norm Standard, it is an
ISO-Standard which means International (no one
excluded).
Again: I am talking here about ISO 12647:
Graphic technology- Process control for the
production of half-tone colour separations,
proof and production prints
Part 2: the offset process, working with AM-Screens at 60 lpi.
Please tell about the good sides, as well as
what is going wrong, and also about your
expectations and the real life in print
production.
best regards / mit freundlichen Gru:ssen
Peter Kleinheider
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From: Neil Barstow <info(a)neilbarstow.co.uk>
Subject: Re: [ECI-EN] Invitation to everyone to get this list going
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Peter
that would be fantastic
an English translation of the German ECI discussions would be very uesful
perhaps an automated online translation service like
http://babelfish.altavista.com/babelfish/tr
wouild get you started, I'm sure it's not going to work for tech words tho.
admin(a)eci.org (ECI.org Admin)::16/11/04::7:18 pm:: GMT+0100
Hi everyone
Indeed, it is very quiet here. It would be great if the posters on the
German site (or some volunteer) could translate these requests into
english so not only the german capable readers and writers can take
usage out of all the information given there.
I also understand that if someone is not fluent in english, or has just
enough practice to read some english lists, might not be able doing
this.
What I will try in the future is to translate the requests as good as
possible into english so a larger discussion could start - and maybe
also I can get better in writing english ;-)
best regards / mit freundlichen Gru:ssen
Peter Kleinheider
ECI-Admin
Best Regards
Neil Barstow
Consulting in Imaging & Colour Management
http://www.colourmanagement.net/
http://www.apple.com/uk/creative/neilbarstow/
11:13 a.m.
New subject: Feedback of ISO 12647-2 users welcome
Hi all
Some comments on Bill Birkett's post:
1. The color of a solid ink depends on the paper,
the ink, and the ink film thickness. When the
color of the paper varies, how does that affect
the intended color of the solid ink?
The ISO standard set Lab values for the paper
types to be used with each
printing condition
2. Color is a three dimensional measure, but the
pressman has just one control, ink film
thickness. Generally, it won't be possible to
achieve the exact color specified by adjusting
ink film thickness. The pressman will have to
estimate the best match, based on three varying
quantities. This will be very frustrating for a
pressman.
There is also a ISO standard for the ink gamut, if the process ink is
not
'in-gamut' to the standard, how will anything match.
3. The tone reproduction curves are shown
graphically, but there is no table or formula
that would enable us to enter values into a CtP
system.
The TVI is what the printing condition and the associated ICC profile is
expecting. Any corrections to the curve on plate output need to be assessed
based on the presses current TVI, measured by printing a test form of 1-100%
tints in all colours, from linear plates, and then adjusted in rip/workflow
to meet the standard.
4. The tone reproduction curves vary with screen
ruling. Is this really a good idea?
I agree, I use process control to adjust the
TVI to meet the standard, from
150 to 225 screen. This work very well. So just differing output curves on
the rip/workflow
5. The tone reproduction curves are specified
using TVI, which is a density based measurement.
So, while the solids are specified
colorimetrically, other values still rely on
densitometry.
Lab values are more accurate then density readings. Once the lab
values have
been matched, a density reading using the 'house' densitometers can be used
on press. The lab values should be checked on an regular basis. Re the TVI,
this is measured after the inks are at the correct Lab values. I guess you
could compile Lab readings for the 4 colours at 5% steps! Interesting
thought?
Regards
Paul Sherfield
The Missing Horse Consultancy Ltd
Telephone: 01442 871752
Mobile: 07899 906385
1:07 a.m.
New subject: Feedback of ISO 12647-2 users welcome
Hi Bill
Am 16.11.2004 um 23:06 schrieb Bill Birkett:
Hello, all. I'm based in the US, and have followed
the work of the
ECI. Being an American, it is my nature to antagonize Europeans with
provocative notions. So here goes :-)
The latest release of ISO-12647-2 specifies solid ink levels with
colorimetry, and specifies tone reproduction curves using graphs.
These changes seem good on the surface, but raise new issues.
1. The color of a solid ink depends on the paper, the ink, and the ink
film thickness. When the color of the paper varies, how does that
affect the intended color of the solid ink?
as already mentioned, there are standard paper types and when using
similar paper, the goal is to reach the aim-values as close as
possible.
When color paper is used, the I usually take a standard profile and
change the paperwhite using tools from Heidelberg or Gretag to generate
a new profile.
Then this printing condition is very close to the standard.
It gets problematic if the paper has TVIs that are far away from the
one in the standard.
2. Color is a three dimensional measure, but the pressman has just one
control, ink film thickness. Generally, it won't be possible to
achieve the exact color specified by adjusting ink film thickness. The
pressman will have to estimate the best match, based on three varying
quantities. This will be very frustrating for a pressman.
for that we have tools like "Best Match" in Gretags SpectreEye, Axis
Control from Heidelberg, ..... (you name it) to find the aim value for
the densities for that papertype. An from there the printer can work
with this density values.
3. The tone reproduction curves are shown graphically, but there is no
table or formula that would enable us to enter values into a CtP
system.
Most CTP Systems allow to enter the aim-value, and the measured value
on print to calculate the correction value. That is also someting that
can be done in a spread-sheet very easily
4. The tone reproduction curves vary with screen ruling. Is this
really a good idea?
What is your thought of it? Shall every screenruling print with the
same TVI? No problem to correct that with CTP-Systems. But at some
point you see artifacts in the print.
5. The tone reproduction curves are specified using TVI, which is a
density based measurement. So, while the solids are specified
colorimetrically, other values still rely on densitometry.
See above. As you already said, there is not so much you can do on a
printing machine. This system has proven to be working well and
measurements can be done very quick.
I set up a proofing system using the FOGRA27 characterization data,
and found some differences compared to typical practice in the US. The
tone curves have lower highlight contrast. I imagine this is due to
the past popularity of positive plates in Europe versus negative
plates in the US. Also, the color balance is a bit cooler. Gray
balance triplets are basically the same in ISO as here, so I can't
explain this difference.
When you compre by numbers what is the difference on the solid inks?
The TVIs are some percent higher - is this the difference you see?
The profiles are based on print with a TVI of 13% in CMY and 17% in K.
To yield the negative plates the measurement values would need to get
recalculated based on the TVI of negative plates and then the result
needs to be compared. Am I correct on this thought?
So, could we use ISO 12647-2 in the US?
We need to bring colorimetry into the pressroom, but with single
valued measurements. Tone reproduction curves could eliminate a great
deal of variation, if used properly. But, TVI is an outdated concept.
We need a better (and simpler) solution for creating TRCs.
Currently, there is no interest whatsoever in color-managed workflows
in the US. The ideas behind PDF/X-3 have no following here. Printers
work with CMYK + spot files. The change from film to CtP has brought
with it color anarchy. Each printer has created their own color
standard, which is based on whatever considerations seem logical to
that firm. It is normal practice for a printer to make their own
proofs of supplied files, then do color corrections before putting a
job on press. Sometimes clients pay for this, otherwise the printer
eats the cost. This is incredibly wasteful, but an accepted practice.
In some cases, quality expectations have dropped to keep costs in
check. In many cases, printing has become a commodity to be bought on
price alone.
So, there is an acute need for standards here, but few comprehend it.
This is a fine example of the "boiled-frog theory." I applaud the
Europeans on their standardization efforts. The Altona test kit is a
great accomplishment. I'd like to see similar work done in the US.
I will comment that later - it is quite late here in Austria
-Bill
Peter Kleinheider
7120
days inactive
7122
days old
eci-en@lists.callassoftware.com
2 comments
3 participants
participants (3)
-
Bill Birkett -
Paul Sherfield -
Peter Kleinheider