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High Pass

High Pass
Filter

Isolates detail by subtracting a blurred copy of the image from the original, producing a mid-gray result where the source is locally flat with bright and dark deviations at edges and texture. Useful for sharpening, frequency separation, and flattening uneven lighting on photographed textures.

Two modes: Per-channel (default) processes R, G, B independently, and Luminance runs the high-pass on luminance only and broadcasts to all channels, which avoids color fringing when delighting textures. Radius range goes up to 500 px so large-radius texture flattening stays interactive.

An optional mask input limits the effect to specific regions of the image.

Parameters

Section titled “Parameters”

Filter

RadiusNumber · px/%
Default: 3.0 Range: 0.1–500.0

Gaussian blur radius for the high-pass extraction; small (1-4)=sharpening, medium (3-15)=frequency separation, large (50-150+)=texture flattening

ModeChoice
Default: Per-channel

Per-channel (R/G/B independent, may produce colored fringes) or Luminance (BT.709 luma only, no color fringes)

  • Per-channelProcess R, G, B independently. May produce colored fringes on saturated edges.
  • LuminanceRun the high-pass on BT.709 luminance only and broadcast to all channels. Avoids color fringing.
Preserve AlphaToggle
Default: true

Pass alpha through unchanged; turn off to high-pass the alpha channel too

Mask

Mask FitChoice
Default: None

Mask sizing

  • NoneCenter the mask at its native size — no resizing. Unmasked regions are unaffected.
  • StretchStretch the mask to exactly match the image dimensions. May distort the mask shape.
  • FitScale the mask to fit inside the image, preserving aspect ratio. Letterboxes where needed.
  • FillScale the mask to fill the image, preserving aspect ratio. Crops edges if aspect ratios differ.
Notes

Output is (Src - Gaussian Blur(Src, Radius)) + 0.5, clamped to [0,1]. Result is mid-gray where the source is locally flat, with bright/dark deviations at edges and texture. Mask Fit only visible when mask is connected.

Pins: image (required), mask (optional). When mask is connected, the effect is blended with the original using the mask (white = full effect, black = original).

Tips

Section titled “Tips”
  • Small radius values (1–4 px) work for sharpening when blended back with Composite in Overlay or Soft Light mode.
  • Medium values (3–15 px) are typical for frequency separation workflows on portraits.
  • Large values (50–150+ px) flatten lighting and shading on photographed textures so they tile cleanly.
  • Use Luminance mode when you only care about detail and don’t want subtle color shifts at edges.
Section titled “Related Nodes”
  • Blur: the inverse operation. Pair with Composite to roll your own sharpen.
  • Sharpen: direct sharpening with a built-in unsharp mask.
  • Local Contrast: clarity-style contrast enhancement.