Sharpening your images
Just before you send an image to print, you can reveal even finer details by using the Unsharp Mask filter.
How sharpening works
All digital cameras are designed with an internal softening filter to prevent antialiasing. This essentially occurs because square pixels don’t do a good job of describing curved shapes in a scene, making them jaggy or staircased instead. To prevent this, the antialiasing filter inside your camera deliberately softens the image by lowering the contrast all over. It’s not your focusing that causes soft images; it’s just the way the camera is designed.
All digital image files therefore benefit from some sharpening before printing, and you will be surprised at the number of hidden details that can appear afterward. The best tool to use is the Unsharp Mask (USM) filter, as its effects can be controlled precisely. The USM works by increasing the contrast at the edges of shapes in your image, but it can be overdone if pushed too far. Always apply the filter as the very last command before printing, because if you edit afterward, its effects will be magnified.
The USM dialog
For simple sharpening, start with the Amount value, shown left, on 50 and leave both Radius and Threshold at 1. On the facing page are five examples of the filter in use, each using different Amount settings. Which one do you think looks best?