Noise Plus Blend

Here's the problem this node exists for: you generate a great face, you run it through an upscaler, and the upscaler helpfully "cleans up" all the skin into a smooth plastic mannequin with velvety fine lines. Flux is especially prone to that plastic look to begin with, and upscaling makes it worse. Noise Plus Blend gets ahead of it - you blend a layer of noise into the image before the upscale denoise pass, and that noise gives the model texture to hold onto instead of smoothing everything into wax.

It's a small, targeted tool, and it's one of those tricks that looks like nothing and then noticeably improves your realism once you start using it.

How it works

The node generates a Gaussian-blurred noise field sized to your input image and blends it in - either across the whole image, or, if you give it a mask, only inside the masked region. Then that lightly-noised image goes into your K-Sampler for the upscale/refine pass at a low-ish denoise. The added grain survives the denoise as micro-texture, which reads as real skin pores or surface detail instead of plastic.

The masking is the pro move. The author's recommended workflow: auto-segment or manually mask just the face (or whatever region is going plastic), noise only that, and leave the smooth bokeh background alone. You keep the dreamy background and the textured skin.

The inputs and outputs that matter

• image - what you're about to upscale.
• noise_scale - how coarse the noise is. Author's range is 0.30-0.50; for AI faces he suggests 0.40-0.50, for landscapes around 0.30.
• blend_opacity - how much noise shows through (0-100). Faces: 15-25. Landscapes: 12-15. Too much and you get visible artifacts; too little and it does nothing.
• mask (optional) - restrict the noise to a region.

Outputs are blended_image_output (feed this into your upscale sampler) and noise_output (the raw noise layer, handy for previewing what you're adding). After blending, the author recommends denoising in your Flux or SDXL sampler at 0.10-0.50.

How to install it

ComfyUI Manager → search ControlAltAI Nodes → install → restart, or:

cd ComfyUI/custom_nodes
git clone https://github.com/gseth/ControlAltAI-Nodes

No downloads - it's a noise generator and a blend.

Common issues

The tuning is the whole game, and the author gives a clean rule: if you're seeing too many artifacts on skin or textures, turn both noise_scale and blend_opacity down; if your upscale still comes out plastic and velvety, turn both up. Start from the face preset (0.40-0.50 / 15-25) and adjust from there.

The other thing: this only helps if there's a denoise pass after it. Noise Plus Blend on its own just makes a grainier image - the magic is the low-denoise sampler pass turning that grain into believable texture. If you want a more advanced version with texture-type presets and color-aware noise, the pack's Perturbation Texture node is the upgrade.