Words and Picture Peter Bargh
If you ever need to scan photographs from a magazine or book you'll notice it's difficult to avoid a weird collections of patterns appearing all over the scan.
These are known as moire patterns and can be reduced.
It's important to remember that scanning other people's photographs is a breach of copyright, but you may have permission or own the material your copying and we have a few tips to help you achieve better results.
Here at ePHOTOzine we occasionally have to take scans from manufacturers' brochures when a product photograph isn't available. To illustrate what we do I've taken a page out of my book Photoshop 6 A to Z and scanned in one of the illustrations.
The obvious first stage would be to place the photograph or book under the scanner and click scan. Here's the result you would get if you didn't make any corrections. Notice the harsh pattern, which shows up mostly in the neutral, non textured, areas.
Scanners usually come with some basic enhancing software offering modes you can set before you scan.
One option is a descreen which helps to reduce the moire pattern. It does this by softening the pattern, but look at what it does to the overall photo! Not recommended.
This example shows how the result can be slightly improved by rotating the artwork to be copied by a few degrees to make it skeewiff on the scanner. Draw the scanning box around the preview photo so that it contains all the picture. Then when the item has been scanned rotate back to horizontal and crop off any unwanted surrounds.
The result is better, but still not good enough.
You can use one of the noise filters - either filter>noise> despeckle or filter>noise> median. Both will reduce the pattern but both are a little like the scanner software and make the overall image lack detail.
We found the best way to achieve satisfactory results is to scan in at a much higher size than required and once the median filter has been applied, at a very low setting, re-size the picture to the desired scale. Then apply the unsharp mask to pull back any loss of sharpness caused by the median filter and re-sizing process.