How to disguise/remove minor moire pattern for magazine image?

[mistercitizen]

What is the best way to do this? Should I just apply a Unsharp Mask, or is there a more refined way of doing this?

Thanks!

 

[Eggles]

I find a slight Gaussian Blur does the job nicely.

 

[ChokingMyTrap]

Sharpening will only make the moiré pattern more apparent. If you zoom right in you can see the makeup of the printing, what you need to do is soften the screen (descreen). The more your blur, the less the pattern, but also the more your image is blurred. You can make it as hard, or easy as you like, all depends on how good you need it for what your doing. You can do it as simple, as just doing a Gaussian blur just enough to remove the pattern, and then using Unsharp mask to get a little sharpness back, but not to much that you bring the pattern back. Sometimes I will work in Lab Colour mode and work in the channels trying to remove noise. Also I now and again I will fade in Median effects.

You can download filters that will descreen, but I find you get better results when you do things yourself.


Cheers

 

[ESquared]

The best possible results I've had for eliminating moire is to scan at extremely high resolution and then resample to a smaller image. This averaged out the colors better than any other method I tried, including descreen and blur.

Theoretically, if you can scan at exactly the correct physical resolution with the document at exactly the correct orientation, (say, 72 dpi or something), you can get no moire pattern. But I found it easier to just scan at 3000 dpi and resample.

Of course, you may not be able to rescan.

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It is better to have honor than a good reputation.
(Reputation is what other people think about you. Honor is what you know about yourself.)

 

[Eggles]

>>But I found it easier to just scan at 3000 dpi and resample<<

Wow - your scanner can do this?

Another trick is to rotate the image slightly prior to scanning - it can be tricky getting the angle right and will vary for different printing processes. But the point is to not try and match the frequency of any of the inks as they are laid down (the CMY and K inks are not all laid down on the paper at the same angle - they vary so that under a magnifying glass, you can see a rosette pattern).

 

[ESquared]

Not physical resolution, but interpolated. The interpolation/resample helps smooth out the pattern without fuzziness more than a blur does.

-------------------------------------
It is better to have honor than a good reputation.
(Reputation is what other people think about you. Honor is what you know about yourself.)

 

[MarcusStringer]

Yeah,
Most of the time I have to scan the image, like I did when I was an apprentice scanning on a old screen scanner to film machine, I have to place the image on about 30 degrees which gets rid of any pattern without having to descreen it.

Marcus

http://www.midlandtypesetters.com.au

 

[ESquared]

If you're looking for the best image quality, though, a software rotation distorts the image by some amount.

-------------------------------------
It is better to have honor than a good reputation.
(Reputation is what other people think about you. Honor is what you know about yourself.)