(Un)Sharpen effects

Unsharp mask is a powerful tool to "sharpen" photos. Contrary to what the name suggests, sharpening does not mean restoring details to an out-of-focus photo. Sharpening refers to the contrast difference between light and dark within an image.

To access the Unsharp Mask tool, select an image on your canvas. 

Click on the Image Filter Effects icon. Click on More Options... to expose more controls, if required.  

Scroll down to Unsharp Mask.

Increase the Radius slider to make bright areas brighter and dark areas darker.  This effect is most visible on the edges of dark and light areas.

Mix controls the degree of intensity of the effect.  Note: if the Radius slider seems inactive, be sure that the Mix value is set above 0.

Threshold affects the interaction of adjacent pixels with more contrast.

The "defog" technique is very effective on black and white images in particular. This will increase contrast on edges to produce great contrasty images.  Set the Radius 200 and the Mix to 0.5 to achieve this effect.

If you plan to use the software's non-destructive sharpening effects, be careful not to pre-sharpen your images in your image editing software. Oversharpening will produce artefacts (stray pixel effects) that are undesirable.