Boosting your Images with the Unsharp Mask.

This is a handy trick for giving your images a bit of contrast boost without needing to fiddle about with Levels or Curves. It's also the way I remove the slight grey caste that appears in jpeg images from my Canon 10D digital SLR.

1. Make sure you are viewing your image at 100% magnification. You can see this at the bottom of the active picture, as shown below.

2. From the Filter Menu, select Sharpen and then Unsharp Mask. The following window will appear.

3. Use the following settings to quickly see what effect this will have on your image.

Amount: 20
Radius: 100
Threshold: 0

Turn the preview option on and off to see the before and after effect, and watch your image and not the little preview window.

4. The key is to leave the Threshold setting at 0 and change the Radius and Amount.
Radius is how many pixels to include and the amount is how much effect to apply. Essentially you are applying a localised contrast to your image, but not as local as actually sharpening.

5. Less is more. I typically use the settings in the window shown in step three.