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Moiré problem....

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  • Moiré problem....

    Hello All,

    Since I realize that my customer may me frequenting this site, I'll keep my language clean and try to retain my civility.

    Problem: Moire in a painting on silk media.

    Files supplied to me: PDF from InDesign

    Several other (same type of images) files for the job have been supplied, and only one has the moire problem.

    Setup: Nexus 8.4 r3, using a basic Raster-Trap WF, proofing thru GMG to Epson 9600.

    Are there any settings in the WF (interpreter, PSTI, etc.) that I can tweak to try to minimize the moire, or am I stuck with what I'm stuck with?

    Thanks for any and all help, it is appreciated.

  • #2
    Re: Moiré problem....

    I use CQS Nominal screening in Nexus and haven't had any moire. I would check the screening. CQS Nominal screening sets the angles different than traditional to get away from moire. Angles in my Nexus 7.5 are C 165 M 45 Y 90 K 105 (where I think the traditional angles are C 105 M 75 Y 90 K 45). When the screens are placed over one another, a rosette pattern should be seen.



    • #3
      Re: Moiré problem....

      Hello, can you see the moire in the PDF before you rip it? Do you see the moire in plates, film?? Let me know where and when you see it. I can help. Alan


      • #4
        Re: Moiré problem....

        Our setup is the same (neuxs) besides the espon is a 9800.

        We use a Paragon Round screening with angles at 153lpi
        Our pantones are mostly on the black screening unless they are not at 100% coverage over a part where there is black. We then set a different the angle (let's say cyan).

        Rarely we come across moiré with those settings. The few times it's happend (if there is a gradient over a large part but not so much color difference or a lot of detail in an image) we have set our lpi to 242 using a Elipse35 screening. The reason why we don't always use this screening is because our dot gain is way to high using this.


        • #5
          Re: Moiré problem....

          oops, a typo. We are also using Epson 9800's.
          Also, using Paragon Euclidean Hole Centered Rosettes at 200 lpi.

          However, I can see the moire in the PDF. So, I finally got the native ID file. I cannot see the moire in the photoshop file, but can see it in ID and every preview along the lines from there on out.

          The ID file I ripped has yielded better results, a much softer, but still visible moire. I have tried changing the angles, etc. etc.

          Right now, I am going to try rotating the file to see what happens next.

          Thanks for all your input.

          - Jeff


          • #6
            Re: Moiré problem....

            The most common trick I use is to output the yellow at a different line screen than the other three colors (y=150, CMK=175). This won't help you if the fabric has a pattern that is conflicting with the screening, but it wouldn't hurt to give it a try.

            If the fabric is yellow or orange, you might try swapping the black and yellow angles or running both at the same angle (which should be 30 degrees from both the cyan and magenta). Typically, moire occurs because the screens of the two or three colors used are not 30 degrees apart. These tricks will work provided the CTs don't have a lot of black in them.

            One thing I've always wanted to try is to run the yellow as a stocastic screen, leaving the other colors traditional.


            • #7
              Re: Moiré problem....

              Well if your seeing the moire on screen, then playing with printing angles isn't going to gain you much if anything. Your seeing the problem BEFORE its getting screened, so screening is not the source of the problem.

              I would try making certain the the image is placed at 100% in IND (scale in PSD as needed) and that Images>Send Data is set to All in IND's print dialog.


              • #8
                Re: Moiré problem....

                Moire is the result of trying to screen a image that has a pattern similar to the screen you are using.
                The silk painting is producing a pattern from the grain of the silk.
                You will be luck to fix this.
                Try using several different screen types that is less like the grain of the silk.
                Trial and error may be the only fix.


                • #9
                  Re: Moiré problem....

                  yes, lucky would be good.
                  I think I'll just put an old-fashioned blur on it and not lose any sleep over it.


                  • #10
                    Re: Moiré problem....

                    I would agree with GinSu. The pattern is the problem, and I would add that it might be a resolution/scaling issue, so do the scaling in Photoshop.

                    You need to:
                    1. See what size the photo is scaled in InDesign.
                    2. Go to Photoshop Image Size, select percent next to width and change size using percentage you get from InDesign. Use bicubic downsample (or try another method if the results are not acceptable using this downsampling method), changing the scale to what it is in InDesign.
                    3. Make sure you can't see the moire when looking at the picture at 100% in Photoshop. If you can see moire here at 100%, the same size you'll place it into InDesign, then you'll have to make it look good here first.
                    4. Place it into InDesign at 100%, preview to make sure it looks good, and then output. If it doesn't look good in InDesign, but does look good in Photoshop, try changing the image type when saving out of Photoshop (e.g. TIF).

                    Let us know how it comes out.



                    • #11
                      Re: Moiré problem....

                      I typically run all my jobs with the yellow as a stochastic. This eliminates all moire in all jobs. Unless of course it was a preprinted image then scanned back in.

                      Running yellow as stochastic works well and since it is yellow you can't see the difference.


                      • #12
                        Re: Moiré problem....

                        Try running your yellow as stochastic. This eliminates all moire problems and since it is yellow, you won't notice the difference.
                        I run all our jobs this way.


                        • #13
                          Re: Moiré problem....

                          > { wrote:}{quote}
                          > Try running your yellow as stochastic. This eliminates all moire problems and since it is yellow, you won't notice the difference.
                          > I run all our jobs this way.

                          Yes! I knew that running the yellow as stochastic was a viable solution, but my pressmen are pansies who can't handle "any of the new fangle computer stuff".


                          • #14
                            Re: Moiré problem....


                            Since we know that a moire is caused by an interference between two or more patterns, and in this case one of the patterns is the weave of the silk depicted, that raises the question of what other patterns are involved in the case of the on screen views in the pdf and the InDesign file? And why not in the on screen view of the Photoshop file? Would scaling the image in the layout have played a role?

                            The only thing that comes to mind is the pattern of screen pixels. If it's that, then it can't be the same moire in the output, since the pattern from the screen pixels has been left behind. Also, if the screen pixel pattern is the second pattern, this should respond to different zoom levels of viewing and/or different monitor resolutions, no?



                            • #15
                              Re: Moiré problem....

                              Right on, Al. I just blurred the mag channel slightly and it's done and over. I don't think all the work in the world would have taken care of this one, it was a problem from the git-go due to the pattern of the silk.

                              Thanks everybody for your input!

                              - Jeff

                              ps. The "pansy" remark about pressmen made my day! Beers on me!


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