FeiFei Film Grain & Tone

People spend whole afternoons prompting "Kodak Portra 400, 35mm". That trick is real - but the cheapest move for making output read as captured rather than generated is a deterministic noise pass that costs ten milliseconds and no model. That's what this node is.

It's not a bloom filter with a random seed. The author clearly owns a camera: the stages run in the order real film does - lens (vignette, lateral chromatic aberration) → film base (halation) → print (S-curve, split tone, micro-contrast) → emulsion (grain) - and grain goes last so the print curve can't crush it. Pure torch, no external models, roughly 0.2s at 1024² on CUDA.

Wire it between VAEDecode and your watermark/save node.

The one decision: mode

mode is a hard switch, not a blend, and this is the single thing to understand about the node.

• Preset (default): the stock in preset drives every effect. All the sliders are ignored - including the five main ones, which stay visible because ComfyUI can't hide widgets. preset_gain is the only strength control you get.
• Custom: the sliders drive everything, and film_type, preset and preset_gain are ignored.

The author deliberately refused a per-parameter mix factor, and that's the right call - with a blend knob you can never tell whether the slider you just moved did anything.

preset_gain scales grain, halation, vignette, print curve, micro-contrast, split tone and colour fringing together, while the stock's own character (grain size, shadow bias, glow threshold) stays put. So 0.5 is a half-strength Tri-X, not half of Tri-X's parameters. 0.0 leaves the image untouched, which makes it a free A/B toggle.

film_type only groups the preset dropdown - it applies no effect of its own. There are 29 stocks across six families (Color Negative, Slide, B&W Negative, Cinema, Special, Other), from Portra 160 and Ektar 100 through Tri-X 400, CineStill 800T, and a "Digital Clean" stock that adds almost nothing and is genuinely useful as a baseline. No preset applies a colour grade; your colours survive, they just look like they were shot on film. Switch film_type without changing preset and it falls back to that family's first stock rather than appearing to do nothing.

The sliders that matter in Custom

Five main ones, and the defaults are well chosen - a real film scan, not a filter:

• grain_amount 0.25 - about ±3.5/255. Past ~0.6 it reads as TV snow. The tooltip says so.
• grain_size 1.0 - clump size, scaled with frame size, so 4K gets physically bigger grain rather than finer.
• halation 0.15 - highlight glow. Push to 0.3–0.6 for the CineStill light-leak look.
• vignette 0.12 - gentle corner falloff.
• tone 0.25 - print S-curve with a small black lift so shadows never reach pure black.

An optional group holds the tuning knobs; three are worth naming. micro_contrast (0.15) is, per its tooltip, the single most effective slider against the waxy AI-skin look. halation_radius (1.0) wants 1.5–2.0 for CineStill-style glow. grain_shadows (0.55) tilts grain into the shadows for a pushed/high-ISO feel.

seed is reproducible - same seed, same grain - and each image in a batch gets seed + index, so a frame sequence doesn't flicker. That detail is the difference between this being usable for animation and not.

Why the grain doesn't look like digital noise

Real silver halide grain is clumped, not independent per pixel. So the noise is generated on a low-resolution grid and bicubic-upscaled, with only about 6% per-pixel detail mixed in, then weighted by luminance - strongest in the midtones, falling off fast in highlights. That 6% is the critical number: crank the per-pixel component and you're back to salt-and-pepper. More informed than the usual torch.randn_like grain nodes.

Output is a single image. One input: image.

Install

ComfyUI Manager → ComfyUI-FeiFei, or:

cd ComfyUI/custom_nodes
git clone https://github.com/aifeifei798/ComfyUI-FeiFei.git
# restart; look under the FeiFei category

No checkpoints, no extra pip installs - the pack's requirements.txt adds only openai>=1.40, and only the LLM nodes use it. This is the best-value node in the pack because it costs you nothing at install time.

Where people get burned

• Grain disappears between the node and the file. 8-bit saving and VAEEncode quantization destroy grain below 1/255. Don't drop grain_amount under ~0.02 and expect to see it - you're writing information the container can't hold.
• Sliders not working. You're in Preset mode. Switch to Custom, or leave the sliders alone and use preset_gain.
• Preset looks nothing like the slider setup you had. Correct - preset and custom never mix. That's the whole contract.
• A workflow saved against an older version needs the node re-picked. preset_mix was replaced by mode and preset_gain, and the widgets were reordered, so old graphs won't line up. Add a fresh node and reconnect.
• RGBA, grayscale, video frames. RGBA keeps alpha untouched, grayscale and 2-channel work, and a frame sequence won't flicker because grain is derived deterministically per index.

If you're chasing photorealism, do this before you go re-rolling seeds.