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Image Sharpening Tool – Unsharp Mask Effect Online

Image Photography image photo sharpen tool
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Drop image here or click to upload Supports JPG, PNG, WebP, GIF – Max 20MB
Upload an image to see the sharpening effect

Frequently Asked Questions

What is Unsharp Mask (USM) sharpening?
Unsharp Mask is a classic image sharpening technique that enhances edge contrast by subtracting a blurred (unsharp) version of the image from the original. Despite its name, it produces a sharper result. Originally developed for film photography darkrooms, it's now a standard digital image processing method used in software like Photoshop, GIMP, and Lightroom.
Why is it called "Unsharp" Mask if it sharpens images?
The name comes from the traditional darkroom technique: a blurred (unsharp) negative mask was physically sandwiched with the original negative during enlargement. This mask cancelled low-frequency information, leaving only high-frequency edge details enhanced in the final print. The "unsharp" refers to the mask being blurry, not the final result.
What does the Radius parameter control?
Radius determines how wide the edge enhancement halo extends, measured in pixels. Small radii (0.5–1.5px) target fine details like hair, eyelashes, and texture. Larger radii (2–5px) affect broader edges and can enhance local contrast. For most photos, 1.0–2.0px works well. Values above 5px create noticeable halos suitable for special effects.
How does the Amount parameter affect the result?
Amount controls the intensity of sharpening, expressed as a percentage. At 100%, the full difference between the original and blurred image is added back. Values of 80–150% are typical for natural-looking results. Going above 200% can create harsh, artificial edges with visible halos. For subtle enhancement, try 50–80%.
What is the Threshold parameter for?
Threshold sets a minimum brightness difference required before sharpening is applied to a pixel. This helps avoid amplifying sensor noise in smooth areas like skies or skin. A value of 0 sharpens everything equally. Values of 2–5 are typical for clean images, while 5–15 helps protect noisy photos. Higher values restrict sharpening to only strong edges.
What are the ideal settings for portrait photos?
For portraits, use conservative settings: Radius 0.8–1.5px, Amount 60–100%, Threshold 3–8. This sharpens eyes and hair while keeping skin smooth. The higher threshold helps avoid accentuating skin texture or blemishes. Focus sharpening on the subject's eyes for the most impactful result.
Can over-sharpening damage my image?
Yes, over-sharpening creates visible white or dark halos around edges, introduces noise in flat areas, and produces an unnatural "crunchy" look. Once applied excessively, the artifacts are baked into the image. Always use the comparison slider to check your results against the original, and consider downloading at slightly conservative settings.
Is this tool free to use? Does it process images on a server?
Yes, this tool is completely free. All image processing happens directly in your browser using HTML5 Canvas technology — no images are ever uploaded to any server. Your files remain private and secure on your device. There are no watermarks, no registration requirements, and no usage limits.
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