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Luminosity Masking

Splits a picture into three soft masks by brightness (shadows, midtones, highlights), the same idea as luminosity masks in Photoshop, so you can grade or retouch just one tonal range.

Luminosity Masking — before / after
In ComfyUI Add Node → ComfyUI-JH-PixelPro → color → Luminosity Masking
Good for Dodge and burn, grading shadows and highlights separately, protecting the highlights, selective sharpening or denoising

When to use it

A luminosity mask selects pixels by how bright they are, not by where they are. That makes it a clean, edge-free selection: lift only the dark areas, cool only the highlights, or sharpen only the midtones, with no cutout to paint.

Here the three masks are soft and add up to 1 at every pixel, so shadows, midtones and highlights blend into each other without gaps or double coverage. You control where the bands change over (shadow_end, highlight_start) and how gradual the transition is (soft_edge).

Quick start

  1. Load Image → Luminosity Masking.
  2. Connect the mask_shadows output to Mask to Image → Preview Image to see the selection.
  3. Use the mask as the mask input of any other node, for example Tone Curve or Color Matcher, to limit its effect to the shadows.

Settings

Setting Default What it does Tip
image required The picture to analyse.
luminance_source lab_l How brightness is measured. lab_l is perceptual (closest to what you see). ycbcr_y is fast and good for live previews. hsv_v is the simple maximum of R, G, B and less perceptual. lab_l for final work.
shadow_end 0.33 (0 to 0.5) Brightness where the shadow band ends. Lower for only the deepest shadows.
highlight_start 0.67 (0.5 to 1.0) Brightness where the highlight band begins. Must be above shadow_end. Raise for only specular highlights.
soft_edge 0.1 (0.01 to 0.3) Width of the smooth transition at both edges. Small gives sharper bands, large gives gentler blends. 0.1 to 0.2 avoids banding in skin.

Outputs: mask_shadows, mask_midtones and mask_highlights, each a soft mask from 0 to 1.

Tips from retouching

  • For dodge and burn, use mask_shadows to lift detail and mask_highlights to bring down blown areas.
  • Keep soft_edge generous (0.15 or more) when masks will gate strong edits, so no tonal boundary shows.
  • Narrow the midtone band (move shadow_end up and highlight_start down) to build a punchy "midtone only" mask for clarity or skin smoothing.
  • Combine two masks with Mask Combine (union, subtract, intersect and more) to make custom ranges such as "darks plus midtones".
  • On large images, ycbcr_y is far quicker than lab_l, so use it for interactive previews and switch to lab_l for the final run.
Under the hood

Brightness is computed in the chosen space: lab_l converts to linear RGB and uses the CIE L* (0 to 1), ycbcr_y the Kornia YCbCr Y channel, hsv_v the maximum channel. Shadows are 1 − smoothstep(shadow_end ± soft_edge/2), highlights are smoothstep(highlight_start ± soft_edge/2), and midtones are what remains (never below 0). The three are then divided by their sum, so they total 1 at every pixel. The code comments report roughly 120 ms for lab_l at 2K on CPU and roughly 7 ms for ycbcr_y at 1024 on CPU; treat these as indicative. shadow_end must be lower than highlight_start, and inputs outside 0..1 are clamped with a logged warning.

Example workflow

Luminosity Masking example workflow. Copy workflows/sample_portrait.jpg into ComfyUI/input/ first.