Who is responsible for moaré

[Magnus]

This is a topic that is seldom discussed. Consider the following scenario:

• Printer gets a print job
• Customers PDF-file is delivered according to specs.
• The printer makes a hard proof or a web proof (screening is not simulated)
• The client review and sign off the proof
• The printer prints the job (all colors are according to the proofs)
• Client receive the final printed product and discover moaré problems that was not visible in the proof

1. Who's to blame?
2. Should a printer take full responsibles and guarantee that no moaré will occur?
3. What tools do the printer got to get notified about a moaré problem before it's going to press?
4. Should the printer do a re-print because of the moaré?
5. How would you as a printer/print buyer handle the situation?

Best regards,

 

[Thomas-Chini]

if you have a problem of moire is surely because you are printing an image that has been scanned from original already printed on off-set

The prepress should report the problem to typography

to avoid the moire there are two systems

1. apply a descreeining being scanned (if the scanner software allows it)
2. Do not apply the descreen but stampre with a modulate screens (FM)

 

[gordo]

Since the moiré was introduced by the printer it is their responibility. Screening moiré can be eliminated with FM screening. It can also be previewed on screen. Check with your workflow vendor as they might have moiré prediction software.

 

[gordo]

if you have a problem of moire is surely because you are printing an image that has been scanned from original already printed on off-set

The prepress should report the problem to typography

to avoid the moire there are two systems

1. apply a descreeining being scanned (if the scanner software allows it)
2. Do not apply the descreen but stampre with a modulate screens (FM)

You're speaking about subject moiré which is not what I think the OP was talking about. Subject moiré would be the customer's fault and cannot be fixed with FM screening.

 

[carlossc_73]

They all are Responsible for Moire, either the Customer and the Printer and the Prepress, and the way to avoid moire when scanning is very simple you just have to rotate somedegrees the original and thats it, the angles of the print wont be translated to the final print.

 

[Magnus]

As Gordo already assumed, the moiré is not caused by a scanned print, it could be a photo of a fabric or a mesh with a certain pattern that interfere with the AM screening. It happens now and then.

I know how the problem can be fixed, you could print with FM screening or do a slight blur/noise in photoshop. But the problem is that it's very hard to predict subject moiré. I am with Gordo that if the problem is presented by the printer, it's the printers responsibility.

So how does the printer get ahead of the problem, is there any moiré prediction software out there that you could implement as a preflight control?

 

[Macmann]

I would lean towards the printer ultimately being responsible to identify and mitigate moiré. Any supplied PDFs or artwork should be reviewed for evidence of re-screened material which will surely moiré. A slight blur in Photoshop will take care of those situations. Other moirés are optically captured by digital cameras and become part of the photograph-those can be subdued in Photoshop as well. Another form of moiré which is not apparent until you are on press is the type that typically appear in fleshtones due to the interaction of the magenta and yellow angles. Those moirés would not be caught on an Epson proof unless you paid for the screening module of your chosen prepress workflow software like Gordo mentioned. In the past we have been asked for charge backs for missing a moiré even though the customer signed off on the press proof. I certainly would not give them the job for free, that being said, how important is the customer to you? They come to us because we are the professionals and we in turn owe it to them to produce the best product possible.

 

[Joe]

Speaking strictly of my workflow, Prinergy, we make screened soft proofs of every job (VPS Proofs) so it is possible we might see the moiré but not a sure thing as a lot of things look to have moiré in a screened proof on a monitor unless viewed at 100% view which is usually too small of an area to notice it anyway. The one sure fire place it should be caught is when it is printed either by the press crew or the QC person. If it gets out the door I believe the printer would be responsible.

If you had a proofing system something like a Kodak Approval which is made from the same screening as the printed job it should be noticeable by the customer before approving. In that case if they approved the proof showing the moiré they would be on the hook for it.

 

[Stephen Marsh]

Responsibility is with prepress/printer. With AM screening we have three angles but four plates, the yellow is generally run with a different LPI than the other plates to help mitigate the issue.

When running a 5th colour that interacts or a two colour job, one of course has to create the correct screen angles.

Gordo has of course written on this subject before:

http://the-print-guide.blogspot.com....en-angles.html

http://the-print-guide.blogspot.com.au/2009/12/moire.html


Stephen Marsh

 

[Magnus]

Ok, It seems like everybody agrees that the printer i responsible for preventing subject moiré. But the solution to prevent seems to be a proof system that could simulate the actual AM screening or viewing bitmap screening preview of each page manually. Or even worse, the printer operator see it in press (bye bye print planning).

his very time consuming and expensive ways of preventing moiré. I can't tell my prepress operators to manually check ripped bitmap data of each page, because then we would be the most expensive and slowest printshop in the country.

There most be a better solution? Do any of you know of a moiré preventing software?

 

[Stephen Marsh]

Ok, It seems like everybody agrees that the printer i responsible for preventing subject moiré.

Magnus, is that a typo in bold? I think that the consensus is simple CMYK screen angle moiré, not subject.

My question to you is, where/why/how is this issue taking place, then you could come up with a solution to avoid the issue.


Stephen Marsh

 

[[email protected]]

Moires are a pain, and no there is no real way to "check if a moire will appear on any given page/file. In the good old days, we used screening systems that not only varied the screen angles, but would vary the DPI of the screen. If a job was say 150 DPI, then yellow would be st 133, Magenta and cyan at 150 DPI, and black was 40% finer like 200 DPI. Even then some textured images would still moire, and only visible when layering all the screened images on a proof. Mories are only seen with screened proofs, so any proofing system that uses simulated con-tone data will never show. In those days, it was the separators problem to solve, but not always so simple. Prepress operators with a lot of experience will certainly raise flags on pages or graphics that lend themselves to be moires sensitive, and extra steps are used to see how offensive the morie becomes. Changing to Fm screening eliminates a lot of moires, but printing FM screening causes it own complexities if it is not a normal standard used by your shop. As much as the digital world has turned a Printing into a science, nothing beats experienced problem solving operators to solve complex problems

 

[gordo]

Thanks Stephen for posting the link to my blog - so I won't repeat that info here. Moiré is a deep subject.
What's key is to identify the nature of the moiré since there are many different kinds (and causes). This thread has shown that there are folks who don't appear to understand this.
IMHO If the moiré is built into the client's file then the client is responsible (the printer is just supposed to reproduce the document without adding or taking away from it).
On the other hand, if the moiré is introduced in the print process (RIPping, or presswork) then the printshop is responsible.
Subject moiré caused by the halftone screening process where the halftone screen harmonically beats with the imagery is, IMHO, the printer's problem. Subject matter where this is a possibility should be red flagged for more indepth proofing. One way is to look at the screened bitmap halftones before they're output to plate if the workflow allows it. The screened image can be looked at on the computer display at 100% and the moiré might be visible (you have to step way back from the screen to scale the image you see in order to see the problem. Sometimes you can scale the halftone lpi by an even factor and, because that would make it a coarse screen which may be reproducible on an inkjet. I.e. if your normal lpi is 150 lpi then, for proofing purposes, output the image of concern at 75 lpi - an lpi at 75 might proof well on an inkjet and let you see if there's going to be a moiré (of course the moiré's frequency will scale according to the lpi - the lower the lpi the lower the moiré frequency).
You could also use an inkjet proofer that can proof halftones (but not all can do this effectively without introducing their own moiré).
I know that some vendors were working on software to predict subject moiré - but where I worked (at Creo) we adopted FM and promoted FM so it wasn't an issue. There is math related to subject moiré so it should be predictable by software. Check with your vendor.

Or you could switch to FM and not worry about it.

 

[Magnus]

Thank you for your answers. It seems like there is a sales oppertunity for a software that predicts moiré.

 

[oxburger]

My question would be, who signed off of the press sheet? Seems to me a foreman or a press operator would have caught it and brought it up before the entire job is printed.


"When a screen hits a screen, that's a moire" (sung to "That's Amore" by Dean Martin)

 

[JoeatData]

My company deals with the same issue from time to time.
Moiré's can be a real pain. There're times you don't see them in the proof, sometimes you don't see them on the plate. There are times you don't see them until the job is on press.
The printer is responsible. It's our job to check/preflight the files.
Our company policy is that we review the pdf and look for potential moiré problems. If we see a potential problem, we inform the customer. We give them the option of fixing these
potential problems or we offer to fix them, these are chargeable fixes. So it's the clients decision of how they want to proceed.

 

[Magnus]

JoeatData, I feel you. The problem is that the control methods is very manual, time consuming and unreliable..