Producing Moire

[ricks]

I had been working on this picture. When I looked at the small preview window in Bridge, it had added a moire effect. I was wondering if there was a way to introduce it in the full size picture. On the web i just find tuts on removing it.

Any suggestions would be appreciated. Thanks, rick

 

[fredlong]

You could try this

How To Add A Moire Effect To A Photograph - ITS

The moire effect is brought about by the juxtaposition of patterns like lines, dots, or similar shapes. This phenomenon often happens in images with

it-s.com

 

[ricks]

Thanks, I had glanced at this before. But tonight I went back and tried again, but could not make much out of it. The screen shots don't seem to relate to one another or to the steps mentioned. Scaling down the image produces the moire shown in my download, but trying to resize to full size loses the pattern. If you can figure out this tutorial, I would appreciate your help. Thanks.

 

[fredlong]

I'm not sure what's going on in that how-to article. I just did a quick search to find it. Your original has a strong pattern so I think you can create the effect just by overlaying slightly a different copy. Since the moire is created by the interference created by overlapping patterns I would start by resizing your image to the expected output size. When looking at any moire you're creating you should be at 100%. Rotate your duplicate layer maybe 1 degree or resize to 99 or 101%. Rotate the layer, not the whole document. Try different blending modes like overlay, soft light and hard light.

Try a little more or less distortion. Maybe shift the upper layer by a pixel after a very tiny resizing. Experiment with opacity. If it looks good in one area but not another just erase the parts you don't like. Maybe different layers for different parts of the photo.

Good luck!

 

[ricks]

Thanks. When I try to resize the smaller image to 100% I lose all the moire. I tried duplicating the original (non-moire) layer resizing and rotating as you suggested.Changing blending modes and opacity gave me some interesting swirl effects but no moire. I thank you for your suggestions. I will have to keep playing with it for a while.

 

[mfturner]

Very interesting experiment! A few additional ideas (that I haven’t tried), a high pass filter should emphasize moire that is already there , but may take some tweaking to get the gain and band pass frequency to useful values. Try very strong values of sharpening maybe (but unsharp mask would take fiddling to get the band pass frequency you want).

Moire isn’t exactly interference, it is aliasing from sampling with higher frequency content than your sampling system can capture (pixel spacing in our case). Most imaging tools will low pass filter the subject matter to keep that from happening, so if you took your image and resampled at a lower frequency (down sampling) you would likely not see it due to the SW “helping” you by low pass filtering. Maybe using a more basic imaging tool like imagemagick or gimp? Matlab or octave or python could resample directly.

Or maybe I’m off in the weeds and someone will correct my gibberish lol, but it’s an interesting experiment, good luck!

 

[ricks]

Thanks for your input. I have been playing with the hi layer from frequency separation, but without much success. Your suggestions of more basic imaging tools are beyond me at this point. Thanks again.