Removing Moire in Photoshop

Moire effect is not precisely common with digital cameras, but it comes about from time to time. In case of too dense patterns which are beyond the resolution capability of your camera, sometimes colored stripes will appear over the image, whose removal is quite a difficult task. The best option is a Photoshop plugin specialized for this end, since there’s no such a function in the software itself. If there’s no plugin at your disposal, there’s still hope that you can do something against the effect. The following method, for example.

Load the photo


The defect in question is quite conspicuous in the photo detail here, called moire. The dense pattern of the faux wood blinds behind the windows caused blue-orange stripes in some areas.

Lab colors

The chief goal is to avoid causing any harm to the details of the picture. You just want to remove the stripes themselves.

Use Image/Mode/LAB color menu to convert your photo to LAB color mode. You’ll see no change in fact, but if you examine the picture channel by channel on the Channels palette, you’ll see that the stripes are gone from Lightness channel, which shows the details, while the stripes are there in “a” and “b” color channels. We’ll have a few rounds with them, but for the time being, click the top “Lab” channel.

Encircled

Zoom in to, say, 300% so that it becomes easier to work on the defected area. Next, select Polygonal Lasso on the toolbar and encircle the defected areas with cautious clicks.

One of them

Go back to Channels panel and select color channel “b”. Stripes here were the most conspicuous.

In Filter menu choose Blur/Surface Blur, and set Radius slider so high when the stripes are gone from the selected area.

The other one

Now repeat the action in color channel “a” after clicking on the name of the channel on the channels panel. Here stripes were a bit less striking, so a little blur will be sufficient.

Stripped of stripes

Having finished the action, go back to Lab channel and see that the extent of Moire has decreased significantly, it’s almost gone even.

Before saving the new picture, don’t forget to switch to RGB color mode in Image/Mode menu.