Unsharp Mask Node

Unsharp Mask applies a technique that blurs the image, compares it with the original and then amplifies the differences. Pixels that differ significantly from the blurred version are treated as edges - they are brightened/contrasted to stand out.

The name is historical: in the film lab, a blurred negative was layered over a sharp positive to create an "unsharp mask" that boosted the edges during printing. Fusion reproduces the method digitally.

It is especially effective at recovering detail in low-contrast images (astrophotography, long exposures, underexposed images).

• Effects Library: Tools > Blur > Unsharp Mask
• Quick add: right-click in the Node Editor → Add Tool > Blur > Unsharp Mask

Three internal steps happen when Unsharp Mask is applied:

1. Blurring the image with a radius set by the Size parameter.
2. Comparison pixel by pixel between the original and the blurred version. Where they differ a lot = edge.
3. Amplification of that difference based on the Gain parameter. Threshold filters out differences that are too small, to avoid amplifying noise.

Result: enhanced edges, uniform areas (sky, smooth skin) left alone - which makes it a much cleaner technique than a global sharpen.

• Input (orange) - required. The 2D image to sharpen.
• Effect Mask (blue) - optional. Limits the effect to an area.

MediaIn → Unsharp Mask → Merge 2D → Saver

Place it early in the chain, after any denoise but before color corrections. Sharpening after the color grade sometimes amplifies artifacts introduced by the grade.

Color Channels (R / G / B / A) (default: all checked)

Turns the sharpen on or off per channel. Unchecking Alpha keeps the silhouette intact.

Lock X/Y (default: checked)

Links horizontal and vertical. Uncheck it for anisotropic sharpening (rare, but possible for images with a dominant orientation).

Size

Radius of the internal blur filter - controls the scale of the details detected as edges. Small Size = fine details (grain, texture). Large Size = broad details (silhouettes, big shapes). Typically 1-3 for digital photos, 5-10 for coarser refinement.

Gain

Strength of the sharpen applied to the detected edges. Controls the amplification. Reasonable values: 0.5-2. Beyond that, white/black halos appear on edges (a sign of oversharpening).

Threshold

Threshold below which an edge is NOT amplified. At 0, every difference (even tiny ones) is sharpened → the noise gets amplified. At 0.05-0.1, only well-defined edges are processed and the noise is preserved. The key parameter for a clean result.

Sharpen

1 parameter (Amount). A fixed convolution filter, non-adjustable radius. No Threshold. Fast but hard to control - it amplifies edges and noise alike.

Unsharp Mask

3 parameters (Size, Gain, Threshold). Fine control over detail scale, strength and threshold. The professional standard for quality sharpening (photo, color grading, film).

Golden rule: for any serious sharpening, prefer Unsharp Mask. Sharpen is only for quick fixes or stylized effects.

• Professional photo sharpening - Size 1-2, Gain 0.8, Threshold 0.05. Brings out the details without touching uniform areas.
• Recovering astrophoto detail - this is the historical use case. It amplifies faint details in nebulae and galaxies without blowing out the background.
• Post-grade compensation - after a color grade that flattened the image, a discreet Unsharp Mask brings back some punch.
• Preparing for a downscale - on an image that will be reduced in resolution, a moderate Unsharp beforehand compensates for the loss of sharpness.
• Final 4K/8K display - a micro sharpen (Gain 0.3-0.5) at the very end improves perceived sharpness on high-resolution screens.
• Avoiding sharpening on uniform areas (skin) - a high Threshold (0.1+) spares the skin and only sharpens the eyes, hair and clothing.

• Threshold is the key to avoid amplifying noise - start at 0.05 and raise it if the noise is still visible in uniform areas.
• Size = scale of the targeted details - a Size of 1 processes the finest details. A Size of 10 processes overall silhouettes. Try several values with a moderate Gain to find the radius that suits your shot.
• High Gain + small Size = halos - classic oversharpening. Lower the Gain, or raise the Size for a softer result.
• Uncheck Alpha to preserve the silhouette (same as the standard Sharpen).
• For film shots, very subtle values (Gain 0.3, Threshold 0.08) are often enough - the eye perceives the enhancement without visible artifacts.
• A Blend on the output lets you mix with the original → you can push the Gain higher and temper it with Blend 50%.
• Apply per channel - on a shot where only the Luma channel should be sharpened (to avoid chromatic aberrations), convert to YUV, sharpen Y only, then convert back.