Everything you need to know about Unsharp Mask
Unsharp Mask (USM) is the industry-standard sharpening technique used in professional photo editing. Despite its name, it sharpens images by subtracting a blurred copy from the original, which enhances edges and fine details while a threshold control prevents noise amplification.
Parameters
- Strength
Controls how much of the sharpened result is blended with the original image. At 0, no sharpening is visible. At 1.0, the full sharpening effect is applied. - Radius
Sets the size of the blur used to create the unsharp mask (0–10 pixels). Smaller radii (1–2) sharpen fine details like texture and grain. Larger radii (4–8) create broader edge contrast, enhancing overall definition and "punch." - Amount
Controls the intensity of the sharpening effect (0–3). Low values (0.5–1.0) provide subtle enhancement. Medium values (1.5–2.0) create noticeable sharpening. High values (2.5–3.0) produce dramatic, aggressive sharpening. - Threshold
Sets the minimum brightness difference required before sharpening is applied (0–0.30). At 0, all edges are sharpened (including noise). Higher values (0.02–0.10) protect smooth areas like skin and sky from being sharpened, reducing noise amplification.
How It Works
The filter creates a Gaussian-blurred version of your image, then calculates the difference between the original and the blur (the "mask"). This difference represents edges and detail. The mask is then added back to the original image, scaled by the amount parameter. The threshold ensures only significant edges are enhanced.
Recommended Settings
- Subtle sharpening – Radius: 1–2, Amount: 0.5–1.0, Threshold: 0.02
- General purpose – Radius: 2, Amount: 1.5, Threshold: 0.02
- Strong sharpening – Radius: 3–4, Amount: 2.0–2.5, Threshold: 0.03
- Portrait (protect skin) – Radius: 2, Amount: 1.0, Threshold: 0.05–0.10
Tips
- Always sharpen as the final step after all other adjustments
- View at 100% zoom to accurately judge sharpening effects
- Use threshold to prevent noise and skin texture from being over-sharpened
- Over-sharpening creates halos – if you see white/dark outlines, reduce amount