Pixelate filters

Sharply define a selection by clumping pixels of similar color values in cells.

Crystallize

Clumps pixels into a solid color in a polygon shape.

Mosaic

Clumps pixels into square blocks. The pixels in a given block are the same color, and the colors of the blocks represent the colors in the selection.

Pointillize

Breaks up the color in an image into randomly placed dots, as in a pointillist painting, and uses the background color as a canvas area between the dots.

Sharpen filters

Focus blurry images by increasing the contrast of adjacent pixels. They include the Sharpen Edges and Unsharp Mask filters, which find and sharpen areas where significant color changes occur (such as the edges). The Unsharp Mask filter is commonly used for high-end color correction.

Unsharp masking, or USM, is a traditional film compositing technique used to sharpen edges in an image. The Unsharp Mask filter corrects blurring introduced during photographing, scanning, resampling, or printing. It is useful for images intended for both print and online viewing.

Unsharp Mask locates pixels that differ from surrounding pixels by the threshold you specify and increases the pixels' contrast by the amount you specify. In addition, you specify the radius of the region to which each pixel is compared. The effects of the Unsharp Mask fUnsharp Mask filter are far more pronounced on-screen than in high-resolution output. If your final destination is print, experiment to determine what settings work best for your image.

Tip: If applying Unsharp Mask makes already bright colors appear overly saturated, convert the image to Lab mode and apply the filter to the Lightness channel only. This sharpens the image without affecting the color components.