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😺NKD Frequency Separate / 😺NKD Frequency Combine

Splits an image into a soft base (low frequency) and a detail layer (high frequency), then puts them back together. The classic job is restoring texture after a relight: you take the pores and the fabric from the original, the lighting from the relit version, and get the relit image back with its micro-detail intact.

image 
flowchart LR
    ORIG(["original"]):::input --> SEP
    SEP["**NKD Frequency Separate**"]:::nkd -- "high_frequency<br/>(its detail)" --> COMB
    RELIT(["relit image"]):::input -- low_frequency --> COMB
    COMB["**NKD Frequency Combine**"]:::nkd --> OUT(["result"]):::output

    classDef nkd fill:#3b3b6b,stroke:#8ab4ff,stroke-width:2px,color:#fff
    classDef input fill:#2d2d2d,stroke:#888,color:#eee
    classDef output fill:#1f4a1f,stroke:#7fd97f,color:#fff
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  • Four ways to build the base. Gaussian is the fast classic, Guided is edge-safe and won't halo, Rolling Guidance erases texture by size while keeping shapes, and Median is for spot blemishes. Radius sets the detail scale.
  • Divide and Subtract are the two detail modes. Divide is a ratio, which makes it lighting-invariant, and that's what makes detail transfer between differently-lit images come out clean.
  • Luminance detail keeps the texture achromatic, so recombining never shifts color. RGB carries chromatic detail as well.
  • linear processes in linear light, which is what gives correct results. Toggle it off for the classic gamma behaviour.
  • mode and linear have to match between the two nodes.
  • The optional mask output confines the detail to a region, skin only for instance.

Preview

The in-node preview has a wipe slider (high frequency ◄ | ► low frequency) so you can see what each layer actually holds. Its blue play button previews even when the source arrives through a resize or a subgraph.

The 1:1 button crops the visible area at native resolution and lets you drag it around. It's the only way to really judge a detail layer, because a fitted view destroys the very high frequency you're trying to look at. When the view is fitted, radius is scaled to that downscale and the hint shows you the effective value (r8 → r2 @ 31%), so the number in front of you matches the frequency you're getting.

← All 😺NKD Basic Tools nodes