moire pattern removal

EM
Posted By
Eric Matthes
Aug 13, 2003
Views
269
Replies
4
Status
Closed
I have a slide of the World Trade Center which produces a moire pattern on scanning. I read a procedure using PS7 to remove moire, but it uses separate color channels. I was wondering if there is a method in PSE to remove the pattern.
I have searched some of the archives, but most of the threads seem to be about scanning from printed media. The pattern disappears when I reduce the size of the image, but I’d like to print near the maximum resolution of the scan, so that method will not really work.
Thank you.
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moire pattern remove

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EM
Eric Matthes
Aug 16, 2003
Carl, Beth,
I just noticed something very interesting. I opened the image to try the method that Carl described. The image opened at 16.7% magnification, and I zoomed to 25% to work on it. The pattern disappeared! Every magnification shows a different pattern, so I think the pattern is coming from monitor issues, not image file issues. I’ll print it later today and let you know what happens. The pattern is not there at 100%, which leads me to believe it will print fine. Moire is a nasty beast. Maybe it will show up at different print sizes.
Beth, I think the methods for avoiding moire during scanning are all related to scanning from print media.
Thank you both!
Eric
EM
Eric Matthes
Aug 17, 2003
I printed a 5×7 and it came out fine. I don’t think it will be an issue at larger sizes either. Thanks again.
CW
Carl Wegner
Aug 17, 2003
Eric,

In case you need it for another problem, Rich’s technique is to improve "posterization", or color banding, which is what I think of when I hear "moire". But maybe I don’t know what "moire" means.

Your change with zoom sounds like aliasing due to dots from printed material (when screen dots & image dots don’t match up & a pattern results due to ignored image dots, effect varies with zoom). Some scanner software has a descreen button for that, but Forum common knowledge is that a small amount of PSE’s Gaussian blur filter generally works better, with more control.

Carl
P
Phosphor
Aug 17, 2003
By the way Eric, I’m sorry but I’d missed you mentioning this was a slide in your original post. Duh. Time to slow down and read things more carefully!

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