Dan Margulis Applied Color Theory

CTPand No Proof

   Date: Tue, 13 Dec 2005 01:46:51 -0000
   From: Stephen Marsh
Subject: CTP and No Proof

So, we are sending out a job that is too big for us to print to a printer with a larger press.

Last time they ran this job, they were film based - now they are CTP.

The digi proof is very different, this 4C blue background (similar to say 280 or Reflex Blue in CMYK) came out very different to the previous film based print, which is the colour target.

So we ran a swatch sheet through their proofer and picked the new blue colour for the background which is close to the old target print.

My boss does not wish to run a new proof, the printer does not care - even though I mentioned that most printers don't like to fly blind with no colour reference and that unless their process control is spot on, and even if it is, a large area of ink coverage (100c 72m 0y 18k) on a double page cover spread is asking for variation among the run (this blue should really be a 5th colour if consistent blue covers are the goal over price).

Apparently the press prints exactly the same as the digital proof indicates (even large *solid* blue 4C backgrounds). I am waiting for the blame game to come around again when the final prints (printed with no composite colour proof to match against).

So, I am waiting to see how good their process control and printing "to the numbers" are, I will gladly eat my hat if this works as they say it does, or will the blue not match and or be all over the shop throughout the print run.

Let's see in a few days what the job looks like, I am taking bets so send through your paypal entry now (just joking). I'll let you all know if I have had a pleasant surprise or not. Ha!

Stephen Marsh.
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   Date: Tue, 13 Dec 2005 08:53:51 -0500
   From: "Dan Remaley"
Subject: RE: CTP and No Proof and No measurement

"blind trust" - "hope" . .  . are these printing terms?

How about measuring?  Purchase a GATF Proof Comparator (#7145D) - send it down the rip on the proofing device and MEASURE the results.  Now, go grab a press sheet (with color bar) and measure it's characteristics. You can check the press sheet against the GRACoL specifications.  You can check the proof attributes at <www.swop.org> it list's the MEASUREMENTS for a 'certified' proof.

NOW, we can talk about whose fault it is. . . . .

Dan Remaley PIA/GATF
Process Control Manager
412.2591814
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   Date: Tue, 13 Dec 2005 08:36:26 EST
   From: Dan Margulis
Subject: Re: CTP and No Proof

Stephen writes,

My boss does not wish to run a new proof, the printer does not care -
even though I mentioned that most printers don't like to fly blind
with no colour reference and that unless their process control is spot
on, and even if it is, a large area of ink coverage (100c 72m 0y 18k)
on a double page cover spread is asking for variation among the run
(this blue should really be a 5th colour if consistent blue covers are
the goal over price).

A proof is of limited use in this situation. Assuming that we're talking about an offset press, large areas that are nearly that solid are going to throw the gray balance off no matter what the pressman does to try to stop it. So, they won't be able to match their own nonimpact proof or anybody else's, except perhaps for the color of the blue itself.

Such jobs, as you note, really cry out for a fifth color. You lose money in the long run by trying to make them work with only four.

Two pieces of advice: first, any images that appear in the same zone as the large solid areas need to be prepared distinctly lighter and warmer than they would be ordinarily, because magenta and cyan will run with higher than normal densities in such areas.

Second, I would reformulate that blue using yellow ink and much less black. If you decide on press that you need to cut back black to try to achieve a brighter blue, the pressman won't be able to accommodate you without turning type gray. If you use yellow, there will be less variability and more possibility for on-press adjustments.

Dan Margulis
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   Date: Tue, 13 Dec 2005 10:47:06 -0500
   From: todie
Subject: Re: CTP and No Proof

On Dec 13, 2005, at 8:36 AM, Dan Margulis wrote:

Two pieces of advice: first, any images that appear in the same zone as the
large solid areas need to be prepared distinctly lighter and warmer than they
would be ordinarily, because magenta and cyan will run with higher than normal
densities in such areas.

Second, I would reformulate that blue using yellow ink and much less black.
If you decide on press that you need to cut back black to try to achieve a
brighter blue, the pressman won't be able to accommodate you without turning type
gray. If you use yellow, there will be less variability and more possibility
for on-press adjustments.

Interesting thoughts (and something I didn't think of in years : )

… also "take-up bars" (or whatever they're called) can (should?) be used, top and/or bottom of the live image area, to reduce "ghosting" (which affects shape and color).
(Man! I've been out of the loop for so long… but I do remember that the fancier jobs were prepared with a separate Black plate for type : )

Laurentiu Todie
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   Date: Tue, 13 Dec 2005 10:12:29 -0600
   From: "Henry Segalini"
Subject: Re: CTP and No Proof

Be careful with a separate black plate for type only.  If the type is too light, the press operator may have even more trouble maintaining proper ink balance.  If we feel this will be an issue we wil add takeoff bars, layout permitting.

Henry Segalini
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   Date: Wed, 14 Dec 2005 09:44:38 -0400
   From: Lee Clawson
Subject: Re: CTP and No Proof

Henry and Laurentiu,
 
What is this "take-up bar" that you both speak of ?? And what does a "take-up bar" do ???

Lee Clawson
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   Date: Wed, 14 Dec 2005 09:45:06 -0600
   From: "Henry Segalini"
Subject: Re: CTP and No Proof

Take up bars are an image on the plate which uses ink from the ink fountain (actually, from the ink train, which is the series of rollers to distribute the ink to the plate) that otherwise would accumulate on the form roller.  This image is not part of the job and is cut off the sheet. The form rollers are the last rollers of the ink train and are the rollers which transfer the ink to the plate.

The two reasons for take up bars that I am familiar with are:

A)  Very light coverage.  If the particular ink unit is not transferring enough ink to the paper, the ink tends to accumulate and the form starts to "scum".  At our place, this is no longer much of a problem because we have high-tech equipment in both pre-press and the press room. We actually, given our equipment, discourage a separate plate for only type.

B) Mechanical ghosting (a.k.a. ink starvation).  This is where, especially in solids, the press is incapable of maintaining an even ink density.  Envision a poster with a solid border and a white box in the middle.  The sides would be pulling ink across the length of the plate.

However, the edges (top and bottom)  would be pulling ink from only the top and the bottom.  So the sides would tend to have less ink available whereas the edges would have more ink available.  So we put take-off bars to even out the ink requirements across the sheet.  Again, this is less of a problem with the new press technology, although we still encounter it.

If this is not clear, please call

Henry Segalini
Universal Printing
St. Louis, MO USA
314.554.9341
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   Date: Wed, 14 Dec 2005 12:24:03 -0500
   From: todie
Subject: Re: CTP and No Proof

that, and…
starvation can be also avoided (or at least one of its results, the sharp ghosting that would occur in the square frame example, ameliorated) by… tilting the layout out of its most likely orientation on plate (edges of frame parallel with the plate's edge).

This results in a situation in which the first cut of the sheet has to be done at an angle (not for the faint of heart : )

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   Date: Wed, 14 Dec 2005 12:23:11 -0400
   From: Lee Clawson
Subject: Re: CTP and No Proof

Henry,

Quite clear. Thank you.

Lee Clawson
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   Date: Thu, 15 Dec 2005 10:42:31 -0000
   From: Stephen Marsh
Subject: Re: CTP and No Proof

Dan Margulis writes:
 
A proof is of limited use in this situation. Assuming that we're
talking about an offset press, large areas that are nearly that solid are
going to throw the gray balance off no matter what the pressman does to try to stop
it. So, they won't be able to match their own nonimpact proof or anybody
else's, except perhaps for the color of the blue itself.
Such jobs, as you note, really cry out for a fifth color. You lose
money in the long run by trying to make them work with only four.

Well, the blue is the most important thing here. It is a corporate profile cover, blue with lighter blue display type and reverse type elsewhere (even more reason to run a 5th colour in an 'ideal world').

There are some small square cut 4C images, they are not the issue. With the lighter seps previously prepared for film the new proofing indicates that the images are going to be brighter and slightly warmer, so this is OK considering the image content.

Two pieces of advice: first, any images that appear in the same zone
as the large solid areas need to be prepared distinctly lighter and warmer
than they would be ordinarily, because magenta and cyan will run with higher
than normal densities in such areas.

Thanks Dan, I was instructed not to touch these and only alter the blue, good advice Dan, I often think of K but not always other inks running too high due to the background.
 
Second, I would reformulate that blue using yellow ink and much less
black. If you decide on press that you need to cut back black to try to
achieve a brighter blue, the pressman won't be able to accommodate you without
turning type gray. If you use yellow, there will be less variability and more
possibility for on-press adjustments.

No time for this now and I did not have time to mix new versions with more Y and less K that were the same LAB value after the test swatch proof was made and the new values chosen for the job as previously stated. The only impact the K will have is on the background blue, with is the majority of the job and some small pictures that I did not separate and I don't know from memory what the GCR is like (I would presume the previous operator used default medium).

I am sure that you are familiar with my type of situation Dan. Small print shop, one person design/art/prepress setting...asked to collect an old job from archive to put on CD to send to another printer for printing. Next thing I hear a few days later is that they are now CTP based and the digital proof shows some major difference than the last time they printed the job (at least they are not dumbing things down to film although that would have helped me here). I make a range of blue colour swatches from differing CMYK mixes and get a small test proof. We pick the swatch that is the closest, attempting to take into account that this will be matte cello glazed which will darken the finish slightly. I adjust the files and send them off again. Despite the whole exercise being to come close to the old blue, all concerned apart from me seem happy that the press will now match the digital proof colour, even if the press operator has no physical target to match as no proof of the job is being made, we had the original proof and a colour swatch proof - but no final proof of the files numbers that are going to press and nothing for the press guy to aim at.

Just another day in the life.

Stephen Marsh.

Lanita