Sharpen Image

Almost every digital photo benefits from a little sharpening. Camera sensors, lens softness, resizing and compression all blur fine detail slightly. The classic remedy, used by photographers since the darkroom era and built into every serious editor, is the unsharp mask. This tool applies it with full control and a before-and-after comparison.

How an unsharp mask works

Despite its name, the technique sharpens. The image is blurred slightly, and the blurred version is subtracted from the original. What remains is the fine edge detail, which is then added back on top, amplified. Light sides of edges get lighter and dark sides darker, so edges look crisper. The three controls decide how strong that boost is, how wide the edges are, and which differences count as edges.

Amount

Amount is the strength, as a percentage of the edge detail added back. The default of 120 percent gives clear but natural sharpening for most photos viewed on screen. Values between 50 and 100 suit portraits; 150 to 250 can work for landscapes and architecture with lots of fine texture. Very high values create the over-processed look of bright outlines along every edge.

Radius

Radius sets how wide the affected edge zone is, in pixels. Small radii between 0.5 and 1.5 bring out fine detail such as hair, fabric and foliage. Larger radii of 3 to 10 increase local contrast and give a punchier, more three-dimensional look, sometimes called clarity. Very large radii are rarely useful except for special effects. For an image that will be printed large, a slightly larger radius than for screen use is common.

Threshold

Threshold protects smooth areas. Differences smaller than the threshold, in brightness levels from 0 to 255, are left alone. A value of 3 to 6 keeps skin, sky and walls smooth while edges are still sharpened. Raise it if grain or noise becomes visible after sharpening.

Brightness only

With “Sharpen brightness only” on, which is the default, the edge boost is applied to lightness and not to individual color channels. That prevents colored fringes, the magenta or green halos that appear along high-contrast edges when each channel is sharpened separately. Turn it off only for special purposes.

Sharpen last

Sharpening should be the final step. Resize first, then sharpen for the output size, because reducing an image changes how sharp it looks. A photo prepared for a 1200-pixel web page needs different settings than one for a large print. Avoid sharpening the same image repeatedly.

Preview and compare

The preview is computed on a reduced copy; the compare switch shows the original. Because sharpening depends on the scale, judge fine detail on the downloaded full-resolution file at 100 percent zoom.

Limits

Sharpening enhances existing detail; it does not invent new detail. Motion blur, missed focus and heavy compression stay visible. For enlarging small images, Upscale Image with its AI model reconstructs plausible detail.

Starting points

For web images reduced from a camera photo, try amount 100 to 150, radius 0.6 to 1 and threshold 2. For portraits, amount 70, radius 1.5 and threshold 6 to keep skin smooth. For landscapes and architecture, amount 150, radius 1 and threshold 0 to 2. For a print at 300 pixels per inch, radius 1.5 to 2 is typical.

Related tools

If an image is noisy, run Denoise Image before sharpening. For the opposite effect, Blur Image softens selected areas. The Image Resizer prepares the output size first.