A Guide to Removing Moire Patterns and Flaws From Scanned Photos

Moiré Reduction
'The Birth of Venus' by Botticelli. Before and after moiré reduction.

S. Chastain

Scanning photos from books, magazines, and newspapers often result in an unsightly interference called a moire pattern. If your scanner doesn't offer de-screening, it's not too hard to remove yourself.

So what's a moire pattern? If you notice a ripple in the pattern of a silk dress or fabric that is a moire. Another example of a moire is one many of us have encountered while watching TV: on comes a character in a loudly-patterned outfit and suddenly your TV screen erupts. It's what happens when patterns collide, and explains why you never see a TV host or news anchor wearing any sort of patterned material.

The most common cause is scanning a printed photograph from a magazine or newspaper. Though you can't see it, that photo is composed of a pattern of dots and your scanner will see that pattern, even if you can't with the naked eye. Luckily, once you've scanned an image, you can use Adobe Photoshop to remove or reduce the moire. 

How to Remove a Moire

  1. Scan the image at a resolution approximately 150-200% higher than what you need for final output. (Just be aware this will result in a massive file size, especially if the image is going to print.) If you have been handed a scanned image containing the moire, skip this step.

  2. Duplicate the layer and select the area of the image with the moire pattern.

  3. Go to Filter > Noise > Median.

  4. Use a radius between 1-3. Typically the higher the quality of the source, the lower the radius can be. Use your own judgment, but you will probably find that 3 works well for newspapers, 2 for magazines, and 1 for books.

  5. Make sure you are zoomed to 100% magnification and apply a small 2-3 pixel Gaussian blur using Filter > Blur > Gaussian Blur.

  6. Go to Filter > Sharpen > Unsharp Mask.

  7. Exact settings will depend on the image resolution, but these settings are a good starting point: Amount 50-100%, Radius 1-3 pixels, Threshold 1-5. Use your eye as the final judge.

  8. With the new layer selected tone down the effect by reducing its opacity to 0 and then increasing the opacity until the moire disappears in the underlying image.

  9. Select Image > Image Size and reduce the resolution of the image.

Tips and Tricks:

  • If you still see a pattern after applying the Median filter, try a slight gaussian blur before resampling. Apply just enough blur to reduce the pattern.
  • If you notice halos or glows in the image after using Unsharp Mask, go to Edit > Fade. Use settings: 50% Opacity, Mode Luminosity. (This is not available in Photoshop Elements.)

Another Quick Approach

There will be occasions where a moire pattern will appear in a photo. This very common in clothing containing a pattern. Here's how you can fix it:

  1. Open the image and add a new layer.

  2. Select the eyedropper tool and select the color of the fabric, not the moire.

  3. Switch to the paintbrush tool and paint over the item with the moire.

  4. With the new layer selected set the Blend Mode to Color.