LC Apply LUT

There are two ways to color-grade an AI image: re-roll it and pray, or apply a lookup table. The LUT is the underrated option - it's a deterministic, millisecond, no-model operation, and the whole post-processing philosophy says reach for the cheap primitive before you burn a diffusion pass. LC Apply LUT is the node that lets you do that in ComfyUI with standard .cube files, the same format every colorist on earth ships.

The mechanism is a genuine 3D LUT, not a tint filter. It parses the .cube file, builds a 3D lattice indexed as [B, G, R] per the Adobe/IRIDAS convention, and interpolates your image through it - every pixel's color is remapped through the table. The pack even ships a self-contained parser so you don't need a second dependency, and on first load it copies its sample LUTs from assets/luts/ into ComfyUI/models/luts/ if they're missing. Note that path: models/luts/ is where you drop your own files, not under custom_nodes. The lut_name dropdown scans that folder, so anything you add there shows up automatically.

Three controls, and the tooltips are worth quoting because they're the author's own voice. strength runs 0–2, "0 = original, 1 = full LUT, >1 overdrives the LUT change (up to 2×). Try 0.7–1.2 for most grades." That's the practical tip: most of the time you don't want the full effect, you want 70–120% of it. log is the one that bites people: it defaults off, and the tooltip is explicit - "OFF for normal photo/sRGB LUTs (recommended). ON only if the LUT is authored for log/linear (inverse-gamma in, gamma out)." This was actually a fix versus an earlier version of this node, which defaulted log on and washed images out. If you're applying a random LUT downloaded from the internet (almost always display-referred), leave it off. If the result looks gray and horrible, then flip log on - that's the tell that the LUT is log-encoded.

The sample list shipped in the pack gives you a taste of the range: AppleLog2_to_Rec709_33_Grid.cube, Kodak_Wratten_85A_.cube, Sony-S-log3-cine-AZ.cube, and a few LC-branded creative ones like LC Cool Breeze.cube and LC_Crushed_Blacks.cube. So even with zero LUT files of your own, you have a dozen looks to play with the day you install.

Where people get burned: putting .cube files in the wrong folder. It has to be ComfyUI/models/luts/ (the node creates it on first run), and the dropdown only lists files there - files sitting in custom_nodes/ComfyUI_LC123_nodes/assets/luts/ won't appear, that's just the sample source. And again: if the grade looks wrong, check log before blaming the LUT.

It's an output node with a single image out, so it terminates a chain (or feeds a save). Install is the pack-standard clone:

cd ComfyUI/custom_nodes
git clone https://github.com/lonecatone23/ComfyUI_LC123_nodes

Restart, and put .cube files in models/luts/. No pip deps, no model downloads. Ten seconds of setup for a color-grading workflow that would otherwise mean leaving ComfyUI for a video editor.