How it works
The Image Sharpener enhances edge clarity and fine detail in photos that appear soft or blurry. It applies an unsharp mask (USM) algorithm — the standard sharpening method used by Photoshop, Lightroom, and professional imaging workflows — entirely in your browser.
Sharpening works by finding edges (areas of rapid pixel value change) and increasing the contrast at those edges. This makes transitions between light and dark areas more abrupt, which the human eye perceives as increased sharpness and detail.
How to use it: upload your image. Set the sharpening amount (1–100) and the radius (the width of the edge enhancement zone). Higher amounts produce more aggressive sharpening. Higher radius affects wider edges. The preview updates in real time. Download the result.
Unsharp mask algorithm: USM creates a slightly blurred version of the image, subtracts it from the original to isolate edges, amplifies those edges by the amount factor, and adds the result back to the original. Despite the counterintuitive name ("unsharp"), this produces sharpening.
When to sharpen: sharpening is most effective on photos that are slightly soft due to camera shake, slow shutter speed, or lens diffraction. It cannot recover a severely out-of-focus image. For best results, sharpen as the last step in the editing workflow — after resizing, color correction, and noise reduction.
Over-sharpening: too much sharpening introduces halos (bright rings around dark edges) and emphasizes noise. At amount > 80 with radius > 3, you'll see these artifacts in the preview. Keep sharpening subtle for realistic results.
Output quality: sharpening increases the apparent detail but also increases file size slightly (more entropy = worse compression). If file size matters, compress after sharpening.
Privacy: the USM computation runs in the browser. No image is uploaded.
Frequently Asked Questions
- Mild camera shake blur can be partially compensated by sharpening, but it cannot fully recover detail that was lost due to motion. Sharpening enhances edge contrast, making slightly soft images appear crisper. Severely motion-blurred images are not recoverable with standard sharpening.
- Amount 40–60, Radius 1.0–1.5 is a good starting point for photos destined for web viewing. Higher amount values add more aggressive edge enhancement. Higher radius values affect broader, softer edges rather than just fine detail.
- Halos are bright rings that appear around dark edges when sharpening is excessive. They occur when the amount is too high relative to the radius. To avoid halos: keep Amount below 80, keep Radius below 2.5, and check the preview at 100% zoom — halos are most visible at full size.
- Sharpen after downscaling. When you downscale an image, the resizing algorithm slightly softens the result. Sharpening after downscaling restores the crispness to the final output dimensions. Sharpening before downscaling and then downscaling again softens your sharpening and wastes the effect.