Demo

A few useful, fundamental filters:

Sharpen > Unsharp Mask...

The primary sharpening filter. This filter increases the contrast at the edge where a light region meets a dark region drawing halos along the edge, darkening the dark side and lightening the light side. Always apply to a separate layer, copied on top of the entire image.

Blur > Gaussian Blur...

The opposite of Unsharp Mask, and the prime blur filter. The radius concerns the number of surrounding pixels to include in calculating an average value.

Blur > Smart Blur...

This filter blurs the tonal fields in an image but not the edges between fields. It can do a good job of reducing grain without softening edges.

Blur > Lens Blur...

This filter creates out-of-focus areas in a way that mimics the optical blur of a camera lens. It can be useful for creating artifical depth-of-field effects (although not as good as getting it right with the camera).

Noise > Add Noise...

This filter randomly varies the brightness of pixels, effectively creating grain. It is useful in collage when you want to match the grain quality of images from different sources.

Noise > Median...

The opposite of Add Noise. This filter reduces noise in an image, rounds off sharp corners, and trims away frizz. It has several practical uses, particularly in conjunction with other filters.

Noise > Reduce Noise...

Also t he opposite of Add Noise. This filter reduces noise in an image, aimed particularly at the type of noise produced by digital cameras, reducing noise while preserving detail.

Other > Maximum...

This expands the light areas in an image, and can be useful in expanding the white portion of a mask.

Other > Minimum...

This is the opposite of minimum; it expands the dark areas of an image, also useful for masks.

Other > Custom...

This is how to create your own filters, which you can save and reload. This method can achieve many effects which are not available in the pre-set filters.

 

Tracing edges with Custom Filters