What sharpening actually does
This page uses an unsharp mask. It blurs the photo’s brightness with a Gaussian of the chosen radius, takes the difference between the original and the blur — the edge detail — and adds part of it back. Each edge gains a slightly lighter side and a slightly darker side, which the eye reads as crisper.
Only brightness is sharpened, not colour, so colour fringes are not amplified. No pixels are added and no detail is recovered: the resolution stays the same, and texture the camera did not record does not appear.
Why a blurry photo will not come back
Motion blur and missed focus spread every point of the scene over many pixels, and the information about where it really was is lost. Sharpening steepens the edges that remain, which helps a slightly soft photo but turns a badly blurred one harsh, with bright outlines.
“Unblur” services guess new detail with a trained AI model, usually on a server. This page does not do that and never uploads your photo. For a slightly soft photo, start with Sharpness 30–60 at Radius 1.0.
Amount, radius and threshold
- Sharpness (0–100) is the strength; 100 adds 1.5 times the edge difference.
- Radius (0.5–3 px) is how wide an edge is treated: 0.5–1 px for fine detail and web images, 1.5–3 px for large prints or soft photos. A larger radius also makes halos wider.
- Threshold (0–20) ignores differences smaller than that many levels out of 255, which keeps skin and sky from turning grainy. The default is 2.
Check at 100% — the preview hides sharpening
The preview is at most 1600 px wide, so a 24-megapixel photo (6000 px wide) appears at about 27% of its size. To keep the preview faithful to the saved file, the radius is scaled the same way: 1 px becomes about 0.27 px on screen, which is almost invisible.
Turn on the 100% view, where one photo pixel is one screen pixel, and click the photo to inspect an area with edges — eyes, text, leaves or hair. Judge the effect there, not in the small preview.
Signs of oversharpening
Bright or dark outlines along edges (halos), grainy skies and skin, and crunchy hair mean the setting is too strong. Lower Sharpness, use a smaller Radius, or raise Threshold.
Printing softens an image slightly, so photos for print can take a little more sharpening than photos for screens. If you plan to shrink the photo, shrink it first and sharpen the smaller version — downscaling afterwards weakens the effect.
Saving a sharpened photo
Sharpen last, after light and colour: sharpening before brightening makes halos stronger. The photo is saved at its original pixel size, up to the device limit.
Save JPG at quality 92 or higher, because lower JPG quality smooths the fine edges you just created. For a photo smaller than 800 px, sharpening cannot add detail that is not there, and the editor says so.