Color Desaturate (MD)

Desaturation seems like the most boring thing a node can do - it's a right-click in every photo editor. But mdColorDesaturateDesaturate is a reminder that "convert to grayscale" has five different answers, and they don't look the same.

The five modes (this is the whole node)

• Luminance - 0.22R + 0.72G + 0.06B, the perceptually-weighted formula. This is the one that matches how bright things look: a green object converts brighter than a red one of equal intensity. It's the default and the right choice for 95% of work.
• Luma - in this implementation the same weights, applied to the non-linearized signal. Luminance vs. luma is a gamma subtlety; here they behave close enough that you won't feel the difference on typical AI output.
• Lightness (HSL) - (max + min) / 2 of the RGB channels. Flatter, softer grayscale; useful when luminance looks too contrasty.
• Avg (HSI Intensity) - (R + G + B) / 3, the plain average. This is the "no opinion" grayscale. Fine for texture work, usually mushier than luminance for photos.
• Value (HSV) - max(R,G,B). The brightest, most contrasty of the five - good for a bold graphic look, bad for preserving tonal subtlety.

The practical lesson: if your B&W looks wrong, it's often not wrong, it's the wrong formula. A flat-looking conversion is usually an Avg or Value result when what you wanted was Luminance. The good news is you can A/B all five in seconds by flipping the Mode dropdown and re-running.

Around it

• image in, image out, optional mask (per-pixel blend strength). RGB and RGBA both work, alpha preserved.
• No other controls. That's the appeal - desaturate is a lookup, not a tuning exercise.

Where it sits

MdColorMod gives you three routes to grayscale and they serve different jobs: this node (fast, formulaic, five presets), the mono mixer (weighted, controllable, for when the result matters), and the extract node (when you actually want a mask out of the color channels, not an image). For the "just desaturate it" case, this is the one you want. It's the kind of deterministic post-pass our post-processing notes argue should live in every finishing workflow - instant, no model, no re-gen required. One thing to know: if "desaturated" is an intermediate step in a bigger grade, desaturating early and re-saturating later is a common way to control the final color pop - this node is the clean first half of that trick.

Installing

The usual:

cd ComfyUI/custom_nodes
git clone https://github.com/MdONeilsl/ComfyUI-MdColorMod

or ComfyUI Manager → "MdColorMod", restart. Empty requirements.txt, pure torch, no downloads, GPL-3.0, and young enough that Manager might not list it yet - clone manually if so.