Dan Margulis Applied
Color Theory
Web vs. Sheetfed Printing
Date: Wed, 25 Jun 2003 12:23:52 -0700
From: Lee Varis
Subject: Web vs Sheetfed
Hi all,
Anyone know the relative percentages of the number of
print jobs going to web presses vs the number of jobs that are sheetfed?
Also... I'm trying to come to grips with the
differences I'm seeing in apparent dot gain between Photoshop's sheetfed
profile and the SWOP profile... are these set up backwards or is the
sheetfed profile just doing too much dot gain compensation?
regards,
Lee Varis
http://www.varis.com
888-964-0024
____________________________________________________________________________
Date: Wed, 25 Jun 2003 16:02:26 -0600
From: Chris Murphy
Subject: Re: Web vs Sheetfed
On Wednesday, June 25, 2003, at 01:23 PM, Lee
Varis wrote:
Anyone know the relative percentages of the number of
print jobs going
to web presses vs the number of jobs that are
sheetfed?
Also... I'm trying to come to grips with the
differences I'm seeing in
apparent dot gain between Photoshop's sheetfed profile
and the SWOP
profile... are these set up backwards or is the
sheetfed profile just
doing too much dot gain compensation?
Hi Lee,
If all things are equal, you will have less dot gain
on sheetfed compared to web fed printing. However, the two profiles
aren't equal. The SWOP profile is based on 133 line screen printing, and
the sheetfed profile is based on 175 line screen. The higher the line
screen, the higher the dot gain.
Chris Murphy
Color Remedies (TM)
____________________________________________________________________________
Date: Wed, 25 Jun 2003 20:07:29 EDT
From: Dan Margulis
Subject: Re: Web vs Sheetfed
Lee Varis writes,
Anyone know the relative percentages of the number of
print jobs going
to web presses vs the number of jobs that are
sheetfed?
It's a trick question. If it's the number of *jobs*,
obviously there are way more jobs printed sheetfed than web, because you
have to be printing at least several thousand copies to make web
economical.
OTOH, if it's the number of *impressions*, obviously
there are way more impressions printed web than sheetfed, because web
presses are capable not just of high speeds but greater page counts
simultaneously, plus with longer runs, there's much less press downtime to
change jobs.
Also... I'm trying to come to grips with the
differences I'm seeing in
apparent dot gain between Photoshop's sheetfed profile
and the SWOP
profile... are these set up backwards or is the
sheetfed profile just
doing too much dot gain compensation?
It could be either one, but the most likely
explanation is that they have them backwards--they simply put the wrong
name on each of the profiles. Either that, or their measurements were even
more screwed up than normal.
Chris's explanation that it's due to line screen is
bogus. The difference in dot gain when going to 175 dots per inch exists
but it's small. The difference between sheetfed and web is huge. In my book
I suggested that it's about 6 points. That's roughly the difference between
the two profiles as they stand, except that the wrong one is the darker
one.
Thus, somebody needs to explain away 2*6=12 points of
additional dot gain to account for how a web profile can produce seps that
are six points *darker* than a sheetfed profile does rather than six points
*lighter* as one would expect. In my book, I suggested that 175-dot per
inch printing adds about one point of dot gain, so that's a start. As soon
as Chris or somebody from Adobe comes up with an adequate excuse for the
other 11 points (and 11 points is huge--almost the difference between web
coated and newspaper printing), I'll believe that they didn't just
accidentally swap the names of the two profiles.
Dan Margulis
____________________________________________________________________________
Date: Thu, 26 Jun 2003 00:29:14 -0400
From: Michael O'Connor
Subject: Re: Web vs Sheetfed
Lee Varis wrote:
Also... I'm trying to come to grips with the
differences I'm seeing in
apparent dot gain between Photoshop's sheetfed profile
and the SWOP
profile... are these set up backwards or is the
sheetfed profile just
doing too much dot gain compensation?
I still think its a combination of factors, higher
screen ruling, higher ink hold out of typical stocks, and typically higher
ink densities used in sheetfed.
If you want a general profile to soft proof expected
results you need to consider more than dot gain alone.
Michael O'Connor
____________________________________________________________________________
Date: Wed, 25 Jun 2003 22:21:47 -0600
From: Chris Murphy
Subject: Re: Web vs Sheetfed
On Wednesday, June 25, 2003, at 06:07 PM, Dan
Margulis wrote:
The difference in dot gain when going to 175 dots per
inch exists but
it's small. The difference between sheetfed and web is
huge. In my
book I suggested that it's about 6 points.
If you don't take line screen or paper into account,
yes it is. Otherwise it's the same process between the two. TR001 is based
on sheetfed press runs, but is the colorimetric aimpoints for SWOP.
In "Quality & Productivity in the Graphic
Arts" Miles Southworth quotes "Rosen test data" as showing
dot gain for 120 lpi @15%. For 150 lpi it was 28%. That's a 13% difference
just due to line screen. At 65 lpi dot gain was negligible at 2%. So there
is clearly an increase in dot gain with increasing screen ruling. HOWEVER,
I'd forgotten the Adobe press run was performed CTP. Dot gain is known to
decrease by as much as 10%. The increase in dot gain going from 133 to 175
is offset to a great degree by the decrease in dot gain by printing CTP,
but not entirely. I propose the remaining difference is due to paper white.
As soon as Chris or somebody from Adobe comes up
with an adequate
excuse for the other 11 points (and 11 points is
huge--almost the
difference between web coated and newspaper printing),
I'll believe
that they didn't just accidentally swap the names of
the two profiles.
That's ridiculous. The SWOP v2 profile exhibits
TR001 behavior (that's
the data that was used to build the profile). I've
confirmed it, and others who depend on SWOP conditions have confirmed it.
That profile is correct.
After doing some digging, here's what's going on
1. Make two LAB documents, fill both with L*=50
2. Convert on of them to SWOP v2, the other to
Sheetfed Coated v2; use *Absolute Colorimetric* in order to preserve the
requested L* exactly.
3. Go into color settings and set the rendering intent
to AbsCol so the eye dropper tool reports actual LAB values instead of
media relative values.
Results:
SWOP v2 = 51C, 40M, 37Y, 6K
Sheetfed = 51C, 42M, 38Y, 5K
Clearly the separation itself is not dramatically
different, if you want the same color accounting for paper white, the
profiles produce similar results. If you make relative colorimetric
conversions, which don't take media white into account, you end up with
darker separations with SWOP v2 than with Sheetfed v2. To simulate SWOP
paper white on Sheetfed Coated takes values of 6C, 5M, 7Y which accounts
for most of the difference.
The reason why a given CMYK image LOOKS darker with
Sheetfed v2 assigned compared to SWOP v2 is again because rendering to the
display is not taking paper white into account. If you take paper white
into account by turning on paper white simulation on both versions, they
end up looking very similar (the SWOP one gets darker).
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Thu, 26 Jun 2003 07:52:54 -0700
From: Lee Varis
Subject: Re: Web vs Sheetfed
On Wednesday, June 25, 2003, at 09:21 PM, Chris
Murphy wrote:
The reason why a given CMYK image LOOKS darker with
Sheetfed v2
assigned compared to SWOP v2 is again because
rendering to the display
is not taking paper white into account. If you take
paper white into
account by turning on paper white simulation on both
versions, they end
up looking very similar (the SWOP one gets darker).
I think I understand this BUT... why should the paper
white point be different if you print to the same kind of paper (coated)?
Shouldn't they display consistently if both have paper white turned off?
regards,
Lee Varis
http://www.varis.com
888-964-0024
____________________________________________________________________________
Date: Thu, 26 Jun 2003 10:26:44 -0600
From: Chris Murphy
Subject: Re: Web vs Sheetfed
On Thursday, June 26, 2003, at 08:52 AM, Lee
Varis wrote:
I think I understand this BUT... why should the paper
white point be
different if you print to the same kind of paper
(coated)? Shouldn't
they display consistently if both have paper white
turned off?
You may be printing to the same kind of paper :) but
SWOP specifies a #5 stock and that's what was used for TR001 (colorimetric
aimpoints for SWOP), and TR001 was used to build the U.S. Web Coated (SWOP)
v2 profile included with Adobe products. The U.S. Sheetfed Coated v2
profile is using either a #1 or #2 stock, I'm not sure which, but the
reported brightness in the profile is pretty white at 97L*, -1a*, 2b*
compared to SWOP which is 89L*, 0a*, 1b*. So these profiles will have
behavior that is the result of their paper white no matter what rendering
intent you use: in the case of AbsCol the paper white is taken into account
in order to get an exact LAB match source to destination. But in the case
of RelCol, the paper white measurement is subtracted such that the CMS
assumes the paper has a whiteness of 100L*, 0a*, 0b*. The result is heavier
separations. Within the current framework there is no way around this as
far as I can tell.
I have a request in to see if TR001 is based on
measurements over a black trap or over multiple sheets of #5. If it's the
former, then TR001 is probably overstating the darkness of #5 stock. That
stock is thin and thus translucent. If placed on a black trap per the ANSI
standard method for taking colorimetric measurements, some of that black
trap will show through and contribute gray component where there is none.
In reality, the way people read magazines, it's paper on multiple sheets of
paper except for the last page in the magazine. That's arguably the way it
should have been measured, even if it's not standard.
If my suspicion is correct, #5 paper white would
probably be closer to 93L*, 0a*,2b*. Maybe even L*=94. That would make a
big difference in closing the gap between the Sheetfed and Web separations.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Thu, 26 Jun 2003 10:53:35 -0700
From: Lee Varis
Subject: Re: Web vs Sheetfed
On Thursday, June 26, 2003, at 09:26 AM, Chris
Murphy wrote:
If my suspicion is correct, #5 paper white would
probably be closer to
93L*, 0a*,2b*. Maybe even L*=94. That would make a big
difference in
closing the gap between the Sheetfed and Web
separations.
OK... I got it! All of this undocumented,
invisible/visible stuff just seems so confusing. It seems much more
straightforward to simply spec total ink, GCR, dot gain and black %... its
just that when recommending separation settings to someone its nice to be
able to say simply, "use U.S.Web Coated (SWOP) v2".
It had always seemed to me that this ended up being
pretty reasonable for the average sheetfed job at a small print shop doing
150 lpi printing. For a real web press job I think it's a tad too dark
whether or not it meets TR001 specs and it has nothing to do with the way
it previews through the soft proof set up.
Now when using the Proof Colors view to visualize your
separations we find that the "standard" CMYK profiles may or may
not match up with your intended paper stock but you have no way of
"switching" the preview to reflect different paper settings. If
you choose not to view "Paper White" the preview , being RelCol,
gives you an improperly skewed brightness regardless... there's NO
perceptual rendering to the screen!
Everyone wants to be able to trust what they see on
screen BUT you still must be very wary... check your numbers and cross your
fingers. A custom press profile is impossible for most users and if you go
down the rather dimly lit path of the Proof Colors view in Photoshop you
could get yourself into some serious dodo!
regards,
Lee Varis
http://www.varis.com
888-964-0024
____________________________________________________________________________
Date: Thu, 26 Jun 2003 15:40:33 -0400
From: Michael O'Connor
Subject: Re: Web vs Sheetfed
I'm out of my element here, but it would seem to me
that adding a mistaken gray component would make the soft proof made to the
web profile darker rather than lighter, so if you took it away there would
be more of a difference between web and sheetfed results, not less, what am
I missing?
It also seems to me that cmyk made to the sheetfed
profile is not darker across the board, its darker from near 3/4 tones to
shadows, where the effects of higher paper grades and higher ink densities
should be appearing.
Michael O'Connor
____________________________________________________________________________
Date: Thu, 26 Jun 2003 15:12:03 -0600
From: Chris Murphy
Subject: Re: Web vs Sheetfed
On Thursday, June 26, 2003, at 01:40 PM, Michael
O'Connor wrote:
I'm out of my element here, but it would seem to me
that adding a mistaken gray
component would make the soft proof made to the web
profile darker rather than
lighter, so if you took it away there would be more of
a difference between web
and sheetfed results, not less, what am I missing?
For the soft proof you are correct. But the effect on
the separations generated by the profile are the opposite. For soft
proofing, you use AbsCol which accounts for paper white. If that paper
white is bogus and darker than it really is, the AbsCol rendering to the
display will predict a darker final product.
BUT because the CMS subtracts the paper white value
when making separations, using the RelCol rendering intent, it's
assuming the paper white is higher than it is, and thus is making heavier
separations than it should. This problem is not a big deal with brighter
papers, but the problem becomes a penalty the darker the paper.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Thu, 26 Jun 2003 15:08:31 -0600
From: Chris Murphy
Subject: Re: Web vs Sheetfed
On Thursday, June 26, 2003, at 11:53 AM, Lee
Varis wrote:
OK... I got it! All of this undocumented,
invisible/visible stuff just
seems so confusing. It seems much more straightforward
to simply spec
total ink, GCR, dot gain and black %... its just that
when recommending
separation settings to someone its nice to be able to
say simply, "use
U.S.Web Coated (SWOP) v2".
There's a lot of room for improvement in both methods.
TAC, GCR, K limit, and dot gain are only part of the tale. The ink colors
themselves play a large role as well and most people using Custom CMYK
don't take the ink colors into account, and merely just change dot gain and
ink limits. Plus there's no simulation possible for white or black since
that architecture assumes white has an L* of 100, and black has an L* of 0.
Both are impossible. It also means black point compensation doesn't work.
It had always seemed to me that this ended up being
pretty reasonable
for the average sheetfed job at a small print shop
doing 150 lpi
printing. For a real web press job I think it's a tad
too dark whether
or not it meets TR001 specs and it has nothing to do
with the way it
previews through the soft proof set up.
That's because of how the CMS makes this assumption
that the paper white is 100 L* when doing RelCol conversions. The darker
the paper, the more gets subtracted from actual measurement data values by
the CMS when using media relative rendering. It's arguably a huge bug in
the ICC spec. What's needed is something like: RelCol rendering for just
highlights and near neutrals, and AbsCol for everything else, but then also
do black point compensation to map the source tonal range into the
destination's tonal range to preserve shadow detail instead of clipping it
(like AbsCol) would. So we really need a new or adaptive rendering intent
to really solve the problem.
I've just heard that the L* for TR001 is artificially
low because they did measure a single 60# sheet on a black trap, not on a
stack of paper. There is a profile in the works using an updated paper
white value. Once I have information on this profile, I'll let you know.
The other thing you could do if you have a profile building application is
to go in an edit the TR001 measurement data white point value and change it
to something like 94, 0, 2 and then rebuild the profile. Then RelCol will
behave better.
Now when using the Proof Colors view to visualize your
separations we
find that the "standard" CMYK profiles may
or may not match up with
your intended paper stock but you have no way of
"switching" the
preview to reflect different paper settings.
Right. With ICC profiles, everything is locked into
the profile. No ability to account for paper white. No ability to account
for changes in dot gain. No ability to account for changes in ink limits or
GCR. No ability to compensate for non-standard lighting conditions. You
have to build separate profiles for each intended purpose.
More and more people are using ICC based color
management, and we're finding increasing limitations with the framework.
Everyone wants to be able to trust what they see on
screen BUT you
still must be very wary... check your numbers and
cross your fingers.
Despite the flaws, it's pretty amazing how well it can
work. But the system is very dependent on having a profile that represents
actual output behavior.
A custom press profile is impossible for most
users and if you go down
the rather dimly lit path of the Proof Colors view in
Photoshop you
could get yourself into some serious dodo!
Yes but it would be like ordering an Approval for a
magazine job and then actually going to press using waterless inks and a
positive plate making process. There are all kinds of ways to hose things
when the wrong assumptions are made. That it's EASY and CHEAP to make the
wrong assumptions with color management is certainly a gotcha (the
consequences of easy and cheap assumptions end up being expensive).
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Fri, 27 Jun 2003 08:03:19 EDT
From: Dan Margulis
Subject: Re: Web vs Sheetfed
Chris writes,
In "Quality & Productivity in the Graphic
Arts" Miles Southworth quotes
"Rosen test data" as showing dot gain for
120 lpi @15%. For 150 lpi it was 28%.
That's a 13% difference just due to line screen. At 65
lpi dot gain was
negligible at 2%.
I don't have access to this document, however, you
must be misinterpreting what Miles said or else he is using some kind of
percentage system that isn't the same as the rest of us use. I would try to
be more reasonable about this, but basically this is the same as if you had
said,
*Miles Southworth has data showing
that the current president of the United States is Rutherford B. Hayes.
*Miles Southworth has found that
the typical human being grows to a height of 213 feet, 9 inches.
*Miles Southworth has a study
indicating that the average summer temperature in Boulder, CO, is 247
degrees below zero.
None of these statements are any more preposterous
than the numbers you're citing, hence it becomes very difficult to discuss
it rationally, but here goes.
*Magazines printed on coated paper almost all use
*either* 150 or 133-line screens, some interchangeably. An ad that prints
in several magazines probably appears a few times at each one. Nobody does
ads twice for the two different settings. If anything even remotely close
to the numbers you cite were happening such a workflow would be out of the
question.
*A common tactic of many authors, including me, is to
run a page on which the same image appears at various different screenings.
This would obviously be impossible if the dot gain difference were that
severe. You do see the effect, but you have to look very, very, very hard.
Certainly the effect is less than a tenth of what you are talking about
above. In my most recent book I have a 150 next to a 300 printing on a web
press that was absolutely never intended to print 300-line screens or
anything close. That's about as extreme a challenge as could possibly be
imagined. I'd estimate the additional dot gain at around 4%--nowhere near
the numbers you're citing for far, far less demanding changes.
*If 65-line screens produce 26% less dot gain than
150-line, that's way more than the 10% or so extra dot gain contributed by
newsprint. Therefore, if you're repurposing a commercial sheet-fed file for
printing in a newspaper, you have to make the image grossly *darker*, to
compensate for the smaller dot gain!!! All those people over the years who
have mistakenly thought that the newspaper seps have to be grossly
*lighter* obviously just don't understand ICC color management!
HOWEVER, I'd forgotten the Adobe press run was
performed CTP. Dot gain is
known to decrease by as much as 10%.
It's not known to do any such thing. SWOP doesn't even
make an allowance for it. My book suggests 3% and shows a sample to back it
up. But, you're right, that would account for a small part of the
difference between the profiles. I'd say you have 8 points to go now, not
11.
I propose the remaining difference is due to paper
white.
If true, it's totally backwards. Judging by the proof
settings, the "web" profile does seem to take a wildly
pessimistic view of how white the paper is. If so, the logical reaction is
to *lighten* the resulting separation, not darken it, as you suggest in a
different post. If the profile is supposed to believe that the web paper is
very dark, it becomes even more difficult to believe, if possible, that it
is generating a sep that's much darker than the corresponding sheetfed sep.
2. Convert on of them to SWOP v2, the other to
Sheetfed Coated v2; use *Absolute Colorimetric* in order to preserve the
requested L* exactly.
Surely you cannot seriously be suggesting using
Absolute Colorimetric in a production setting.
This whole conversation is as simple as it is
ludicrous. Any digital file is going to appear darker if printed on a web
press than on a sheetfed press under almost any conceivable condition.
Logically, therefore, one must expect a web profile to generate a
significantly *lighter* sep than a sheetfed profile--especially so, if the
paper is supposedly dark. Instead, we get a profile that generates a
significantly *darker* sep.
We do not need a discussion of tristimulus values,
rendering intents, L*a*b*, colorimetry, ICC politics, how newspaper
printing actually has less dot gain than sheetfed printing, or the square
root of pi here. What we need is a for the web sep to be lighter than the
sheetfed sep.
Since this is apparently too onerous a request, you
offer us 1) that, according to color science, web printing is actually
*lighter* than sheetfed printing, so we need a darker sep; 2) that you can,
if not give us a lighter sep, then at least one equally dark, provided we
are willing to accept an extreme cyan cast and not have our 0c0m0y areas
0c0m0y any more.
Now, refresh my memory. Why, exactly, does ICC color
management have such a bad rep?
Dan Margulis
____________________________________________________________________________
Date: Fri, 27 Jun 2003 07:46:34 -0600
From: Jim Donovan
Subject: Re: Web vs Sheetfed
outstanding answer dan!!!!! once again you hit the
nail on the head. thanx
for keeping it real life, not theroy, hard to believe
anyone who puts dots
on paper could disagree. thanx!!!!!
____________________________________________________________________________
Date: Mon, 30 Jun 2003 13:28:58 -0600
From: Chris Murphy
Subject: Re: Web vs Sheetfed
On Friday, June 27, 2003, at 06:03 AM, Dan
Margulis wrote:
I don't have access to this document, however, you
must be misinterpreting
what Miles said or else he is using some kind of
percentage system that isn't
the same as the rest of us use.
I quote from page 14-18 "A 65-line screen has
almost no dot gain, while a 150-line screen has considerable dot gain. It
would be foolhardy to increase the frequency to more than 150 lpi, because
in most cases that would cause extreme dot gain. Some printers are capable
of printing finer screen rulings, but only with special attention to
blankets, ink viscosity and tack, and critical ink and water balance. When
printing too fine a screen ruling, press crews have to keep middletones and
shadow open by reducing the SID."
This would be for film based plate making, in 1989.
The soft dot produced on film makes it more susceptible to dot gain during
plate making, thus it stands to reason the higher the line screen the
bigger the dot gain problem. CTP/DTP have a sharp dot, and with linear
plate making the dot you ask for is the dot you get regardless of line
screen.
In any event, I've now provided two citations. It's
not an acceptable form of debate to simply make jokes in a lame and
unconvincing attempt to discredit something you don't even have access to.
If you are going to make the claim that the data I've cited is wrong, you
need to provide contrary credible evidence that specifically refutes what
I've cited.
*Magazines printed on coated paper almost all use
*either* 150 or 133-line
screens, some interchangeably. An ad that prints in
several magazines probably
appears a few times at each one. Nobody does ads twice
for the two different
settings. If anything even remotely close to the
numbers you cite were happening
such a workflow would be out of the question.
If it weren't for transfer curves and reducing SID
yes. Transfer curves have been used for years to compensate for dot gain in
order to ensure file portability specifically in the example you cite.
*A common tactic of many authors, including me, is to
run a page on which the
same image appears at various different screenings.
This would obviously be
impossible if the dot gain difference were that
severe.
That you are doing this at 300 lpi implies CTP and the
difference in gain due to plate making is zero, unlike with film based
plate making. You assume the difference is the same regardless of line
screen. I don't.
*If 65-line screens produce 26% less dot gain than
150-line, that's way more
than the 10% or so extra dot gain contributed by
newsprint. Therefore, if
you're repurposing a commercial sheet-fed file for
printing in a newspaper, you
have to make the image grossly *darker*, to compensate
for the smaller dot
gain!!!
1. Who prints 65 lpi on newsprint these days? SNAP
calls for 32% dot gain @ 85 lpi.
2. You presume that there is only 10% extra dot gain
contributed by newsprint. Due to the lower dot gain of 85 lpi, the actual
contribution to dot gain by paper is a lot higher than you are
proposing, in my opinion. The whole point of printing at 85 lpi on
newsprint instead of 150 lpi is because dot gain would be out of control at
150 lpi on newsprint. That's why there is such a thing as printing at lower
line screens on lower quality papers. If the difference were just a few
percent, as you are suggesting, then we could all print 175 lpi on any
paper we wanted.
HOWEVER, I'd forgotten the Adobe press run was
performed CTP. Dot gain is
known to decrease by as much as 10%.
It's not known to do any such thing. SWOP doesn't even
make an allowance for
it. My book suggests 3% and shows a sample to back it
up.
SWOP accounts for it by tying TR001 colorimetric
behavior to SWOP. That is the target response. SWOP doesn't care if your
dot gain is 2% or 30% so long as you hit the colorimetric aim points, and
visual comparison to the proof.
I propose the remaining difference is due to paper
white.
If true, it's totally backwards. Judging by the proof
settings, the "web"
profile does seem to take a wildly pessimistic view of
how white the paper is. If
so, the logical reaction is to *lighten* the resulting
separation, not darken
it, as you suggest in a different post.
In that different post, I explicitly said that this
only happens with the RelCol intent, and why: because RelCol doesn't take
the paper white into account. It assumes paper white has an L* of 100. So
it ends up making heavier separations than it should, and the problem gets
worse with decreasing paper white L*.
Surely you cannot seriously be suggesting using
Absolute Colorimetric
in a production setting.
It depends on what your doing. If you want an exact
match of something, and using AbsCol won't induce undesirable clipping,
then yes that it the rendering intent to use. That's the definition of the
intent. If you have an image where AbsCol would induce undesirable
clipping, or simulate a source white that isn't desirable (like a D65 white
point from the Adobe RGB (1998) profile), then obviously that's not the
correct intent to use.
The example was only to show that to match a given
approximately midtone neutral value of L* 50, 0*a, 0b* you get about the
same separation if you use AbsCol which accounts for paper white; and to
demonstrate that your assertion the two profiles have had their names
swapped is wrong.
Now, refresh my memory. Why, exactly, does ICC color
management have such a
bad rep?
Because you make a mountain out of a mole hill. There
are numerous flaws with ICC based color management, nearly all of which are
well documented, and it works very well despite those flaws. The problem of
darker separations occurring when paper white points are low is something
that is easily dealt with in one of two ways: 1.) Use perceptual rendering
which most vendors add a contrast boost in order to compensate for this
very problem; since this is the intent to be used with lower gamut and
lower dynamic range output device, it's possibly a more appropriate
rendering intent. 2.) Use soft proofing with paper white and ink black
simulation. If you do this, you would know visually that the separation is
going to be darker even before you've done the separation.
However, per usual you prefer to complain about it
rather than offer a solution. What kind of color management do you propose
as an alternative to the ICC based color management you demonize, Dan?
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
From: "Remaley, Dan"
Date: Tue, 1 Jul 2003 08:42:39 -0400
Subject: [colortheory] RE: dot gain Web Vs Sheetfed
I believe there is a little confusion on what 'dot
gain' is, or 'tone value increase' as the professionals like to call it. In
the film based world a linearized film output i.e. 50% dot became 56% on
plate, (some shops became 60%), because of the plate exposure. In the past
we never measured the values on the plate. The total gain (by the way, this
is a DENSITY measurement of solid Vs tint), therefore, you can get a dot
gain number from a proof that doesn't have dots! The website
www.swop.org has all the gain numbers and Lab numbers for SWOP certified
proofs.
This gain number represents the TOTAL gain, optical
and mechanical. Optical gain is caused by the light being reflected or
absorbed by the substrate. Mechanical gain is the absorption of ink into
the paper and physical attributes during platemaking. Coated paper less
gain, un-coated higher gain.
A study, done here at GATF by Mr. John Lind,
concluded that CTP dots print no different than conventional dots of the
same value with film made plates. The lower gains of CTP is related to
physical dot size on the plate. Remember the 3M Matchprint material, the
staple of proofing in the past? It had very little physical gain, but a lot
of optical gain. Take a 10 power loupe and compare the size of the dot on
this proof and the same area on the press sheet - the press sheet dot is
much larger - then why do they 'look' the same? Optical gain! When the
gains are close the color matches, at least in film based, - with digital -
all bets are off! Be aware that plate dot readers only measure the physical
size of the dot (no optical gain).
I am in the process of measuring the dot size of film
based plates exposed correctly (6-8 micron), at 100-133-150-175-200 line
screens, I can tell you that the dot size (on the plate) increases in
relationship to the line screen. A 50% dot at 100 line measure 56% at 200
line 62%. My next step is to print these values and measure the total gain.
I'll present this information at Tech Alert in January.
Dan Remaley
Process Control Mgr.
Graphic Arts Technical Foundation
412.741.6860x450
____________________________________________________________________________
From: Dan Margulis
Date: Tue, 1 Jul 2003 12:27:07 EDT
Subject: Re: [colortheory] Web vs Sheetfed
Chris Murphy writes,
I quote from page 14-18 "A 65-line screen has
almost no dot gain, while
a 150-line screen has considerable dot gain. It would
be foolhardy to
increase the frequency to more than 150 lpi, because
in most cases that
would cause extreme dot gain. Some printers are
capable of printing
finer screen rulings, but only with special attention
to blankets, ink
viscosity and tack, and critical ink and water
balance. "
This is a recognized industry expert with considerable
printing credentials. Yet you are quoting him as saying that 175-line
printing is nearly impossible due to excessive dot gain!!! The mind
boggles. Surely, even a color management consultant must be aware that
175-line printing is completely standard now, and can probably be found at
your local mom-and-pop sheetfed house. Can't you do some simple detective
work, to figure out how such an authority could say something so obviously,
utterly, and blatantly ridiculous?
Permit me to help. What Miles said was quite correct.
Dot gain *is* extreme, and printing very difficult, at 175-line screens, IF
YOU ARE MAKING YOUR SEPS ON A PROCESS CAMERA!!!! This information antedates
drum scanning! He isn't even using today's definitions of dot gains,
because they weren't standard until long after he wrote what you quoted.
The films he was writing about were exposed through both a filter and a
screen--their dot structure is analog and soft-edged, and it doesn't behave
anything like the hard-edged digital dots of any device commonly used to
output film or plates for the last 20 years.
In any event, I've now provided two citations. It's
not an acceptable
form of debate to simply make jokes in a lame and
unconvincing attempt
to discredit something you don't even have access to.
If you are going
to make the claim that the data I've cited is wrong,
you need to
provide contrary credible evidence that specifically
refutes what I've cited.
It depends on how ludicrous the claim is, as I was
attempting to point out. If your post says, I have a noted authority who
states that even on today's modern roads, it's difficult to drive from New
York to Philadelphia in less than three days, nobody needs to waste time
refuting this. Now, even worse, you've posted your complete quote, which in
effect says, it takes that long because you have to stop frequently to feed
and water the horses.
[Re: why some magazines can print at 133-line screen
and others use the
same file for 150-line with no noticeable difference
in darkness.] If it weren't
for transfer curves and reducing SID yes. Transfer
curves have been used for
years to compensate for dot gain in order to ensure
file portability
specifically in the example you cite.
Transfer curves haven't been used "for
years" in the magazine industry because all digital-to-plate workflows
didn't make their appearance in the magazine industry until quite recently,
and they aren't completely standard even yet. Transfer curves do not affect
existing pieces of film.
For nearly two decades, the standard and exclusive
practice was for specialized prepress houses to generate film, often
creating as many as a dozen different versions for various magazines. The
versions were all imaged from the same file, but with one of eight
different output possibilities: positive or negative; RREU or RRED; and 133
or 150 screen. There was NO compensation for dot gain applied; if you
looked at two negs from three feet away you wouldn't be able to see any
difference as to which was 133 as opposed to 150.
The prehistoric figures you supplied would have made
such a workflow absolutely impossible, yet substantially every magazine in
North America did it.
[Re: the example in my book showing the same image
output at various line
screens, with limited differences in dot gain] That
you are doing this at 300
lpi implies CTP and the difference in gain due to
plate making is zero, unlike
with film based plate making.
I think you should check with platesetter
manufacturers before making such a bald statement, because most if not all
of them either can't do 300-line screens and/or mix screen rulings on the
same page. Yes, 99% of my book was printed direct-to-plate, but that page
was done in film, because it had to be.
However, per usual you prefer to complain about it
rather than offer a
solution. What kind of color management do you propose
as an
alternative to the ICC based color management you
demonize, Dan?
I did not complain, criticize, or demonize it. I said
it had a bad rep. If you're asking how to improve it's bad rep, I would
suggest that those proponents of it who have very little practical
experience should refrain from making pronouncements about things that they
don't understand, such as the difference between camera and scanner dots,
the historical screening practices of magazines, or the capabilities of
modern platesetters.
This thread concerns two methods of separation, one
for an idealized web press and the other for idealized sheetfed. Anybody
with more than a month or so of pressroom experience knows that the
sheetfed sep needs to be significantly darker, period, no talk about
measurements, no talk about rendering intents, no politics, no ISO
standards. Just significantly darker, please.
Instead, this method makes the sheetfed sep
significantly *lighter* than the web sep. This is such an obviously
ridiculous outcome that anybody who tries to defend it calls anything else
they might say on the topic of printing into question. The experienced
person simply says, "something is seriously screwed up here."
Why can't you?
Dan Margulis
____________________________________________________________________________
Date: Tue, 1 Jul 2003 15:01:54 -0600
From: Chris Murphy
Subject: Re: Web vs Sheetfed
Dan, don't have a cow. I had already put it into
context by date. The fact of the matter is, there is a correlation between
increasing line screen and increasing dot gain that exceeds your estimate,
in my opinion.
Now, even worse, you've
posted your complete quote, which in effect says, it
takes that long because
you have to stop frequently to feed and water the
horses.
I see your tactic: make believe that I've made some
outlandish claim and ignore the context I put it it, and then give birth to
one or more bovines while typing your response. Cute.
Here is something recent, from David Q. McDowell, who
is involved in various CGATS subcommittees and standards processes:
"A piece of dot gain trivia that usually astounds
most people is as follows:
1 If you assume dot gain is basically movement of the
edge of the dot
2 Then a change from a 49 percent dot to a 50
percent dot of a 133 l/in round dot screen tint is a movement of the edge
of the dot of 0.7 microns (change in dot radius)
3 Typical ink film thickness are 0.7 to 1.2
microns.
Doesn't take much squishing or spread of the dot to
change size. Also even with CTP it doesn't take much beam spread to
change dot size."
Tell me why we don't print 150 line on newsprint, Dan.
If exceptional dot gain, beyond your few percent suggestion is NOT the
reason, I'd like to hear it. While you're at it, I'd like to hear your
explanation for the correlation between paper quality and line screen. The
lower the paper quality the lower the line screen is. If it has nothing to
do with dot gain, why is there such a correlation? Hmm?
If you're asking how to improve it's bad rep, I would
suggest that those proponents
of it who have very little practical experience should
refrain from making
pronouncements about things that they don't
understand, such as the difference
between camera and scanner dots, the historical
screening practices of
magazines, or the capabilities of modern platesetters.
Oh that's impressive spin, Dan. I'm definitely not on
par with either your skill or apparently your experience in this regard.
The experienced person simply says, "something is
seriously screwed
up here." Why can't you?
I explained why it was screwed up from the get go,
higher gain for 175 lpi printing causes the sheetfed profile to produce
lighter separations; and known behavior for RelCol assuming paper white is
L*=100 causes that intent to be increasingly ineffective for making
separations with decreasing real paper whiteness. You deny both. In the
first case, I've had a handful of people print 175 line screen on a #2
stock using the sheetfed profile and said it went OK. In the second, now
there is something not deniable. Relative colorimetric doesn't take paper
white into account, Absolute colorimetric does, yet you tried to argue even
that point and say I was wrong.
Keep on denying it all Dan. I await Dan Remaley's
results in the meantime.
Now the profiles that are screwed up are Web Uncoated
and Sheetfed Uncoated - which are identical profiles only differing in
name.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
From: Dan Margulis
Subject: [colortheory] Re: Web vs. Sheetfed
Chris Murphy writes,
Tell me why we don't print 150 line on newsprint, Dan.
If exceptional
dot gain, beyond your few percent suggestion is NOT
the reason, I'd
like to hear it. While you're at it, I'd like to hear
your explanation
for the correlation between paper quality and line
screen. The lower
the paper quality the lower the line screen is. If it
has nothing to do
with dot gain, why is there such a correlation?
http://www.ledet.com/margulis/PP7_Ch15_Resolution.pdf
has what you're looking for. A brief excerpt:
"Anyone who thinks that if a fine screen is good,
then a finer one must be better, is a moron. The finer the screen ruling,
the smaller the dots, but the smaller the dots, the harder they are to
print properly. If they are on the cusp of what the press can tolerate, the
following irritating things happen.
Darker areas start to plug up, resulting
in a perceived lower maximum shadow.
The minimum acceptable highlight dot
goes up; at some point, a dot simply gets too tiny for the plate and the
blanket to hold. Overall, detail in the highlight will become inconsistent.
The image will begin to appear soft as
transition areas become less distinct.
Dot gain will appear to increase.
Now, at what point does all this unpleasantness start
to kick in? In newspaper printing, as a rule, it happens at about 100, so
most newspapers print with an 85-line screen, and 65-line is not uncommon.
Some, however, do use a 100-line screen, and I know of at least one that
has successfully used 120 lines."
In the previous chapter, there is a nice graphic
showing what happens when the screen ruling is higher than the printing
conditions should tolerate--nice closeup of what's happening to the dots,
next to a closeup of dots from the same file printed direct-to-plate, next
to normal-sized versions of both.
The average person would call the result a color
shift, not excessive dot gain. If the effect were even worse, the result
would probably be called posterized before it would be called excessive dot
gain.
Dan Margulis
____________________________________________________________________________
Date: Fri, 04 Jul 2003 17:25:32 -0000
From: "Dave Marley"
Subject: Re: dot gain Web vs. Sheetfed
Dan Remaley wrote:
I am in the process of measuring the dot size of
film based plates
exposed correctly (6-8 micron), at
100-133-150-175-200 line screens, I can
tell you that the dot size (on the plate)
increases in relationship to the
line screen. A 50% dot at 100 line measure 56%
at 200 line 62%.
In general, these values seem reasonable. They
are much more reasonable than Dr. Southworth's hard-and-fast
conclusions about the relation between dot gain and screen
resolution. Dan Margulis's observations about dot gain correspond vastly
more accurately to the experiences of high-quality lithographers.
Regarding plate gain in particular, there is
quite a bit of variation in plate quality just there is in other
material or equipment. For example, several years ago I worked at a
small book printer that specialized in fine-line duotone
reproduction. We were testing new plates with camera-generated,
drop-out, 300-line film. We found significant differences between
plates from different manufacturers -- as much as ten percent
variation in the midtones and three-quarter tones. Surprisingly, the
plates with the least gain also held the finest highlight dot. This
problem required camera negs to be duped to eliminate the vignette on
scum dots.
The point I'm making is there are many
significant variables in dot gain. Chris Murphy defers to unreliable
or out-of-context conclusions when he derides the standard trade wisdom
presented by Dan Margulis.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
Three weeks later, the thread resumes.
Date: Wed, 30 Jul 2003 00:50:40 -0000
From: "John Luke"
Subject: Photoshop SWOP and sheetfed reversed?
Don't laugh, but I read a post on the Rob Galbraith
forum that indicated someone thought the Photoshop CMYK values for USWeb
Coated (SWOP) v2 and US Sheetfed Coated v2 were reversed. Urban
legend or what? And in which version of Photoshop?
John Luke
____________________________________________________________________________
Date: Thu, 31 Jul 2003 12:25:38 -0600
From: Chris Murphy
Subject: Re: Subject: Photoshop SWOP and sheetfed
reversed?
On Wednesday, July 30, 2003, at 09:14 PM,
Jonathan Clymer wrote:
The ink limits of these two profiles, relative to each
other, don't make
sense to me and I asked about it on this forum about
six months ago. Check
the archives and you will see a long discussion, again
on this forum, more
recently.
How do they not make sense? The sheetfed profile as a
350% TAC and the webfed profile has a 300% TAC.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Fri, 01 Aug 2003 22:07:38 -0400
From: Jonathan Clymer
Subject: Re: Subject: Photoshop SWOP and sheetfed
reversed?
Oops! Sloppy writing on my part! It's been a while
since I've used either of these profiles. It isn't the ink limit that had
me worried, it was the gain.
By the way, I went back to the original question I
posed, which was further into the past than I remembered (in fact, I was
shocked to see how much further). Here it is, with Dan's reply:
Jonathan writes,
Also, why are the grey values for web higher than
sheetfed, when the
expectation for dot gain is higher for web?
The only logical explanation, which I have previously
suggested to my good
friends at Adobe, is that when these two profiles were
placed in Photoshop,
some knucklehead transposed their names. The sheetfed
profile in fact does a
pretty good job of making web separations, and vice
versa.
As you and Dan Remaley note, dot gain is distinctly
higher in web than
sheetfed printing, regardless of screen. A separation
generated for web
should be lighter than one for sheetfed, period. These
two profiles have it
backwards.
If you must use these profiles, the workaround is,
while shaking the head and
rolling the eyes, to assume that the one labeled
"sheetfed" is really web,
and the one labeled web sheetfed.
Dan Margulis
(message 2808, May 8, 2002)
Since that time I have used only the Custom dialogue
box to set values for my CMYK seps (even though that is a primitive (!)
method according to Adobe expert Chris Cox).
Jonathan Clymer
____________________________________________________________________________
Date: Sat, 2 Aug 2003 01:41:18 EDT
From: Dan Margulis
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
Jonathan quotes me as saying,
The only logical explanation, which I have previously
suggested to my good
friends at Adobe, is that when these two profiles were
placed in Photoshop,
some knucklehead transposed their names.
Evidently I'm going to have to withdraw that
statement. As noted by Chris Murphy, the sheetfed profile has a total ink
limit of around 350%, which is way too high for web work, and in fact
wouldn't be accepted by certain sheetfed printers. The web profile has a
more normal 300% limit.
Still, the idea that a sheetfed profile should produce
a lighter separation than a web profile is absurd, so all we can say is
that there was something seriously deranged in the way that these two
profiles were produced.
Personally, I stick with Custom CMYK as Jonathan does.
I'd be happy to switch over as soon as the Photoshop team gives us the
ability to edit the profiles within Photoshop.
Dan Margulis
____________________________________________________________________________
Date: Sat, 2 Aug 2003 09:36:27 -0400
From: John Castronovo
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
From: <Dan Margulis>
Personally, I stick with Custom CMYK as Jonathan does.
I'd be happy to switch
over as soon as the Photoshop team gives us the
ability to edit theprofiles
within Photoshop.
I recently heard that Kodak has a plugin to accomplish
just that. I have no reports, pro or con, about it yet.
Have you heard of it?
http:
//www.kodak.com/global/en/professional/products/software/colorFlow/customColor/customColor.jhtml?id=
0.3.8.38.3.4.6&lc=en
____________________________________________________________________________
Date: Sat, 2 Aug 2003 13:28:56 -0600
From: Chris Murphy
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
On Friday, August 1, 2003, at 08:07 PM, Jonathan
Clymer wrote:
Oops! Sloppy writing on my part! It's been a while
since I've used either of
these profiles. It isn't the ink limit that had me
worried, it was the gain.
The gain between them is virtually identical. The
problem comes when using relative colorimetric with SWOP, which causes the
CMS to assume paper white is L*=100 instead of actual paper white, so it
makes SWOP separations heavier than they should be. This came up barely a
month ago on this forum.
Since that time I have used only the Custom dialogue
box to set values for
my CMYK seps (even though that is a primitive (!)
method according to
Adobe expert Chris Cox).
It is rudimentary but if you give it good information
it can make good profiles. The problem is most people accept the default
ink hues which are not based on TR 001 even though the default says it's
using SWOP. And they also plug in a single dot gain value, which causes
Photoshop to presume that dot gain for MYK only, and 4% higher than that
for C. So the separations are less than ideal than if correct data were
plugged into it.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Sat, 2 Aug 2003 13:37:39 -0600
From: Chris Murphy
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
On Friday, August 1, 2003, at 11:41 PM, Dan
Margulis wrote:
Still, the idea that a sheetfed profile should produce
a lighter separation
than a web profile is absurd, so all we can say is
that there was something
seriously deranged in the way that these two profiles
were produced.
Considering the huge variation possible in sheetfed
printing compared to publication printing, I think that's a big assumption
to make. There are seriously deranged print behaviors. The problem as I see
it is in the name and presentation of this profile as though there is a
generic sheetfed profile for the U.S. There are many dozens of such
behaviors not even counting for the different kinds of paper stocks and
coatings used.
But to suggest it is an invalid profile, in the sense
that it cannot represent a sheetfed coated print behavior is simply false
because it is based on an actual press run. We can debate its value in
specific situations all we want but I do know of instances where it has
worked for printing on #2 stock at 175+lpi printing CTP. As a matter
of fact I just had a postcard printed, and the printer requested that I use
this profile. (Which I'll point out while it seems to have made an
acceptable separation, it seriously overestimated the ability of the press
to produce saturated blues.)
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Sat, 2 Aug 2003 13:41:23 -0600
From: Chris Murphy
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
On Saturday, August 2, 2003, at 07:36 AM, john
c. wrote:
I recently heard that Kodak has a plugin to accomplish
just that. I
have no reports, pro or con, about it yet.
Despite their web site suggesting that the latest
version of Photoshop is 5.0, the current version does still work in
Photoshop 7 when running on OS 9.x or in Classic on OS X. But it will
not work in Photoshop 7 running natively in X, and will break
entirely with the next version of Photoshop which will be Mac OS X
only.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Sat, 2 Aug 2003 19:59:33 -0400
From: John Castronovo
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
Well, all that is fixable. Did it work well enough to
be ported over to OS
X? I think a beta is in the works.
john castronovo
____________________________________________________________________________
Date: Sat, 2 Aug 2003 20:21:28 -0400
From: Dan Margulis
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
John Castronovo writes,
Have you heard of it?
Yes, I have it, but it's creakier than I am--it
antedates Photoshop 5 and hasn't been updated AFAIK. It consists of two
pieces, one very expensive and perhaps no longer available, being a
full-fledged profile editor, the other being a plug-in that allows
Photoshop users to generate a new profile by means of applying curves and
such to an image until it looks good, whereupon the plug-in figures out and
generates whatever profile is needed to implement those changes. The
plug-in, as I recall, can in effect change dot gain settings, but it can't
effectively change black generation, which is one of the main reasons one
would want to use it. For that, the expensive product is needed.
I preferred to work with the expensive product but for
some people the plug-in might be better. I have no problem with it, but
obviously I'm not going to write or teach about a third-party product in
any depth.
Dan Margulis
____________________________________________________________________________
Date: Sat, 2 Aug 2003 22:30:55 -0600
From: Chris Murphy
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
On Saturday, August 2, 2003, at 05:59 PM,
john c. wrote:
Well, all that is fixable. Did it work well enough to
be ported over to OS
X? I think a beta is in the works.
I still use it. But this is the first I've heard there
is any color management product development going on at Kodak, let alone
something in beta. Do you have more information or a contact person?
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
____________________________________________________________________________
Date: Mon, 04 Aug 2003 03:21:07 -0400
From: Michael O'Connor
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
I'm curious. Has anyone actually run films of an image
converted to each profile and then read the films? Absolute colorimetric
doesn't seem to me to really alleviate this, sheetfed still reads lighter,
especially where most gain should be expected. I still think something else
is going on here, and I don't think, at root, its a mistake, or at least
not a simple one.
Also, are you sure the TAC on sheetfed 2 is 350%? It
seemed to me to be 330%, and that would relate perfectly to the ShOPS
proposal from GATF. From the apparent timing of the release of the proposal
I'd think that Adobe probably referenced it while developing the sheetfed 2
profile, and its also interesting in that the mean variations in sheetfed
printing aren't as great as you might think.
Michael O'Connor
____________________________________________________________________________
Date: Mon, 4 Aug 2003 10:37:53 -0600
From: Chris Murphy
Subject: Re: Re: Subject: Photoshop SWOP and sheetfed
reversed?
On Monday, August 4, 2003, at 01:21 AM, Michael
O'Connor wrote:
I'm curious. Has anyone actually run films of an image
converted to
each profile and then read the films? Absolute
colorimetric doesn't seem to me to really alleviate
this, sheetfed
still reads lighter, especially where most gain
should be expected. I still think something else is
going on here, and
I don't think, at root, its a mistake, or at
least not a simple one.
The mistake is not in the data in the profile. That's
based on an actual press run. It's legitimate to complain that the behavior
defined in the U.S. Sheetfed Coated v2 profile is "unique" and
that more common behaviors for sheetfed printing exist. It's legitimate to
complain about the naming of this profile that implies it's suitable for
"printing on a coated sheetfed litho press in the U.S." and that
there appears to be no documentation for the actual behavior of this press.
Also, are you sure the TAC on sheetfed 2 is 350%?
Yes. RGB 0,0,0 and LAB 0,0,0 both produce a 350% TAC
with this profile.
It seemed to me to be 330%, and that would relate
perfectly to the
ShOPS proposal from GATF. From the apparent timing of
the release of
the proposal I'd think that Adobe probably
referenced it while developing the sheetfed 2 profile,
and its also
interesting in that the mean variations in
sheetfed printing aren't as great as you might think.
I disagree. There's a reason why there are many
printers who can't match a Matchprint to save their life, and other
printers who don't like Waterproofs or Color Arts or Pressmatches and the
increasing use of digital proofing systems. Presses don't have the same
behavior. A couple of years ago, the last time I had checked, there were
more than 30 different Matchprints that could be produced just in terms of
the different laminates and standard base materials, NOT accounting for
differences in exposure. There are at least two commonly used magenta ink
hues used in the U.S. as well.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
Adobe Photoshop training classes are taught in the US by Sterling Ledet & Associates, Inc.