Everything you need to know about Surface Blur
Surface Blur smooths flat areas of an image while preserving sharp edges and fine details. It uses a bilateral filtering approach that considers both spatial distance and color similarity, making it ideal for noise reduction, skin retouching, and preparing images for laser engraving.
Parameters
- Radius
Controls the size of the blur neighborhood (0–10 px). Higher values sample more surrounding pixels, producing stronger smoothing on flat surfaces. At 0, no blurring is applied. Values of 3–5 work well for subtle smoothing; 7–10 for heavier noise reduction. - Threshold
Sets the color similarity tolerance (1–100%). Pixels within this color distance from the center pixel are blurred together; pixels beyond it are left sharp. Low values (5–15%) preserve most edges and only smooth very similar colors. High values (40–100%) blur across more color differences, approaching a standard blur.
How It Works
For each pixel, the filter examines neighboring pixels within the radius. Each neighbor receives a weight based on two factors: how close it is spatially (Gaussian falloff) and how similar its color is to the center pixel. Neighbors with very different colors receive near-zero weight, so edges between distinct regions stay crisp while uniform areas are smoothed.
Tips
- Use low threshold (5–15%) to reduce noise while keeping all edges intact
- Use higher threshold (30–50%) to smooth out texture while keeping major contours
- Great as a pre-processing step before dithering or edge detection for cleaner results
- For skin retouching, try radius 4–6 with threshold 15–25%
- Combine with Sharpen afterwards to restore fine detail if needed