Frequency Separation Linear Light

This is the sibling to RES4LYF's Frequency Separation Hard Light node, doing the same job - splitting an image into a low-frequency layer (color, tone, broad lighting) and a high-frequency layer (fine texture and detail) so you can edit or swap them independently - but recombining the two with a different blend mode. Frequency separation itself is old news to photo retouchers: it's the standard way to smooth skin tone without losing pore detail, or fix a lighting shift without wrecking texture, and RES4LYF just brings the trick into a ComfyUI graph. Linear Light is generally the gentler of the two recombination modes - it tends to reconstruct tonal values more faithfully than Hard Light, at the cost of being more sensitive to clipping if your high-pass layer has extreme values in it.

Where you'd reach for it in a generation workflow: after any pass where the model changed lighting or color grade but you want to preserve the original's real texture - a relit portrait, a style-transferred image where you'd rather keep the source's actual skin/fabric/surface detail, or compositing a masked guide region back into a larger image without a visible seam.

How the ports work

Same design as its Hard Light sibling - every port is optional, and the node figures out which direction you're using based on what's wired:

• Separate: feed original in, get high_pass and low_pass out.
• Recombine: feed high_pass and low_pass in (after editing one or both), get a reconstructed original out, this time using Linear Light math instead of Hard Light.

There's no explicit mode toggle - it's read from which ports you've connected.

Installing it

Bundled with the full RES4LYF pack:

• ComfyUI Manager - search "RES4LYF," install, restart.
• Manual - cd ComfyUI/custom_nodes && git clone https://github.com/ClownsharkBatwing/RES4LYF, then cd RES4LYF && pip install -r requirements.txt, restart.

No model downloads needed; this node is pure image compositing.

Common issues

Not sure which of the two to use. Try Linear Light first if you want a subtler, more tonally accurate recombination; switch to Hard Light if the result looks flat or you want more punch. Neither is objectively better - it depends on your source image and how aggressive the edit between separation and recombination was.

Wrong ports wired. Since every port is both an input and an output on this node, it's easy to accidentally leave original connected when you meant to recombine, or forget to connect both high_pass and low_pass. The pack doesn't document expected behavior for a partially-wired node, so treat separation and recombination as two distinct wiring patterns and don't mix them in one instance.

Reconstructed image has visible banding or odd tonal shifts. Linear Light math is more sensitive to values outside a normal range than Hard Light is - if your high-pass layer got clipped or pushed to extremes by whatever edited it, that shows up more here. If you see this, either back off the edit strength on the high-pass layer or switch to the Hard Light variant, which tolerates a wider range more gracefully.