Moire pattern on final product

Started by zacgil, September 10, 2014, 11:41:22 AM

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zacgil

Hey All,

I've encountered a problem with a Moire pattern showing up on a product.  It's a comic book that was designed using half-tone dots throughout the publication.  It's a compilation of designers so only a specific artist's section turned into an obvious almost checkerboard moire pattern.  It did not show up on the proofs or even when looking at Kodaks Virtual Proofs.  I've attached an image of the VPS proofs and one of the final product. 

I want to know if it's something that can be fixed on the prepress side of things or if there are tips I can give the designer to help this not happen in the future.

Any info is helpful!

Thanks
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zacgil

I am a punky, sophisticated lesbian (or something similar).

DCurry

I've run into similar issues in the past - one possibility is the halftone dots are not 1-bit scans. If they are 8-bit gray scale scans, then your RIP applies screening to it to, it creates moiré.

By making the illustrations 1-bit, you are removing any elements of gray that would get screened by the RIP, thereby eliminating moiré possibility.
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born2print

One solution may be plating with FM screening (Stacatto)
that's basically why the epson proofs did not show the pattern.
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Joe

Quote from: DCurry on September 10, 2014, 12:19:54 PMI've run into similar issues in the past - one possibility is the halftone dots are not 1-bit scans. If they are 8-bit gray scale scans, then your RIP applies screening to it to, it creates moiré.

By making the illustrations 1-bit, you are removing any elements of gray that would get screened by the RIP, thereby eliminating moiré possibility.

Yep...screening a screen = moire.
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zacgil

Okay, gotcha.  Thanks for the replies. 

It's making more sense now.  If they keep the halftone areas at 100% then that gets rid of the need to screen a screen.

It's a pretty awesome comic book, so anything I can do to help this not happen in the future is perfect.   
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Diddler

If you old brain remembers, You can also try changing the screen angles to a different angle on output.
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DCurry

Quote from: zacgil on September 10, 2014, 02:13:44 PMIf they keep the halftone areas at 100% then that gets rid of the need to screen a screen. 

It's not just keeping it at 100% - it MUST be 1-bit (Bitmap mode in Photoshop). I emphasize this because you could have a grayscale halftone pattern where the center of the dots measure 100%, but at the very edges you have anti-aliasing which smooths out the edges by blurring them slightly, resulting in grays at the edges. These grays are what will get screened, producing the moiré.
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Farabomb

Quote from: Diddler on September 10, 2014, 07:33:50 PMIf you old brain remembers, You can also try changing the screen angles to a different angle on output.

This was my first thought but since it was just one element of the book I thought that if you did that the morie would show up in the other images.
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DigitalCrapShoveler

It's not just the anti-aliasing, any dot reproduced with a color break is going to moiré. The problem is, the dot from the art conflicts with the halftone dots from the screening. The best thing to do, would be to knock the art slightly out of focus. The effect will be visible without a doubt, but better than a moiré.
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DigiCorn

In a pinch, I've scanned at a high a rez as possible, run the gaussian blur, and then the unsharpen mask.
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zacgil

So, we have another Comic Book coming through the shop with a big Halftone image on the front.  I've linked the Post-Trap/Ink Optimized PDF.   The question is, is there anyway I can tell how it will come off the press?  I've read through the rest of the comments and understand how it can be fixed on the design side of things, but is there a process I can put the file through that will accurately show how it will be screened on plate?  Or, is it doomed and I should tell the customer that he will most likely have a big, ugly moire on his cover?

https://www.dropbox.com/s/9fw2sbu9p1jo3ho/Halftone_Cover.pdf?dl=0
I am a punky, sophisticated lesbian (or something similar).

David

do you have the ability to preview the 1 bit tiff plate file?
We have a copy of Creo Copydot Toolkit we use to preview the 1 bit tiff (it can take all the separations and combine them together).
We can see the screening, trapping, etc.
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David

what line screen do you normally output these at?
I can rip the file you posted over and see if I can get a screen cap of it to show you the moire.
I can see it already on the monitor here when I view your pdf.
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