Moire pattern on final product

ZacGil

Member
Hi 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
 

Attachments

  • Screen shot 2014-09-10 at 8.42.12 AM.jpg
    Screen shot 2014-09-10 at 8.42.12 AM.jpg
    42.2 KB · Views: 219
  • photo.JPG
    photo.JPG
    3.8 MB · Views: 205
Hi 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

If the art is supplied already halftone screened then the supplied art has to be at a dpi that is a multiple of the dpi of the output device (e.g. for a 2400 dpi plate setter the dpi of the art can be 2400 dpi, 1200 dpi, 600 dpi etc.). If it's not then you will get moiré.

If the art is supplied already halftone screened but that area is not at 100% then the RIP will screen the screen and you will get moiré.
 
Awesome, thanks for the information.

I do have one question. What do you mean "if the area is not 100%"?
 
Awesome, thanks for the information.

I do have one question. What do you mean "if the area is not 100%"?

See attached. Left side is halftoned - right side is halftoned but not 100%.

I can't see the original art clearly as it's too small so it's hard to see if the moiré is coming from the two issues I've described.

PS I've seen the first problem quite often with cartooning software made in Europe (2540 dpi) being output on 2400 dpi devices in Hong Kong.
 

Attachments

  • Screened.jpg
    Screened.jpg
    333.9 KB · Views: 197
Last edited:
Ahh I see. I'll definitely let them know about the DPI potential issue. But I think you may be right about it not being 100% in those areas.

I've attached a screenshot of the same image, just much more zoomed in. Both of these, tree and pants, produced an obvious pattern, just slightly different in the final product.
 

Attachments

  • Screen shot 2014-09-10 at 11.07.49 AM.jpg
    Screen shot 2014-09-10 at 11.07.49 AM.jpg
    24.6 KB · Views: 214
Ahh I see. I'll definitely let them know about the DPI potential issue. But I think you may be right about it not being 100% in those areas.

I've attached a screenshot of the same image, just much more zoomed in. Both of these, tree and pants, produced an obvious pattern, just slightly different in the final product.

Yup, the patterns are different because the original tones are different. Your problem is definitely the second one that I described - it may also include and be compounded by the first one.
 
Google descreen Photoshop and you will find a step by step fix. Or you could have the job scanned as copydot (which is bitmap image)
 
Google descreen Photoshop and you will find a step by step fix. Or you could have the job scanned as copydot (which is bitmap image)

The methods that I've been able to find for descreening via Google don't work. Do you have a link that does?
I don't see how scanning as a copydot would have any value. Maybe you can explain?
 
What resolution were the VPS files ripped at?

Were they viewed at 1:1 or 100% view, 50% or 25% view or some other non proportional view etc?

Did you view each separation, or just the composite?

Knowing that the original files had halftone screens, you would have to take care that the new screen angles did not clash - or to remove angle issues by using FM screening rather than traditional AM screening.


Stephen Marsh
 
Last edited:
As an aside point, if you supply a crop of the area that has moiré as C, M, Y & K plate anlged/dot 1-bit separated TIFF files at 2400 or 2540ppi, I will run them through an inkjet proofing RIP to see if moiré is shown. Contact me via a PM if you are interested, I can supply a FTP link etc.


Stephen Marsh
 
Last edited:
The methods that I've been able to find for descreening via Google don't work. Do you have a link that does?
I don't see how scanning as a copydot would have any value. Maybe you can explain?

I have never tried the descreening options in Photoshop. I would think they would improve the output but cartoons sometimes have such a low screen LPI that it probably wont work. The copydot option is usually scanning film as bitmap images and merging into DCS2 format. The bitmap image doesn't get screened at RIP
 
The VPS files are RIPd at 90lpi. We go to plate at 150. I've just looked at the 150 VPS and didn't see anything that would have tipped me off on their either. I've looked at the separations as well.

As for the screen angles, would it be possible for us to let them know what angles we use and therefore help them in the design process? Is that information worth anything to them on that end of things? Also, is there a way for me to mimic our angles in order to see if this will be a problem on press?
 

PressWise

A 30-day Fix for Managed Chaos

As any print professional knows, printing can be managed chaos. Software that solves multiple problems and provides measurable and monetizable value has a direct impact on the bottom-line.

“We reduced order entry costs by about 40%.” Significant savings in a shop that turns about 500 jobs a month.


Learn how…….

   
Back
Top