Simple Gamma Adjust

Extracted maps are never the right brightness the first time. Roughness comes out too dark, albedo comes out washed out, height comes out too flat. Simple Gamma Adjust is the smallest possible fix for that: one image in, one gamma slider, one image out. There's nothing else, and that's the point.

How it works

Gamma correction is output = input ^ gamma applied per channel. The behavior flips around 1.0:

• gamma below 1.0 brightens - a 0.5 gamma lifts midtones hard while leaving black alone.
• gamma above 1.0 darkens - 2.0 crushes midtones down.
• gamma exactly 1.0 is a passthrough, no change.

Because it's a per-pixel power function, it works on whatever you feed it - grayscale maps, RGB albedo, height, roughness, metallic. It won't clip highlights the way a brightness multiply can, and it affects midtones more than shadows, which is why it feels "natural" compared to a straight image * 1.5.

The range is 0.1 to 5.0, so there's plenty of travel, and the step is 0.01 - you can dial in a 1.13 that exactly fixes a slightly-dark albedo without overshooting.

The honest take

This is a utility node, not a feature node, and that's fine. Where it earns its keep is in the middle of a PBR chain: the pack's own extractor literature talks about gamma-tweaking metallic/roughness contrast, and this is the convenient knob for doing that on individual maps before you combine them. Use it to match the brightness of maps from different sources, or to push a roughness map into a better range for your engine's shading model.

Installing it

Part of amtarr/ComfyUI-TextureAlchemy - ComfyUI Manager "Texture Alchemy", or:

cd ComfyUI/custom_nodes
git clone https://github.com/amtarr/ComfyUI-TextureAlchemy

Restart, then right-click → Add Node → Texture Alchemist → Adjustment. No dependencies, no models - one torch.pow on ComfyUI's bundled PyTorch.

Where people get burned

Two things. First, the input is clamped to 0–1 before the power is applied, so if you're feeding it an HDR or EXR texture with values above 1.0, you'll lose that headroom before the gamma ever runs. Second, because gamma is a power curve, the same gamma that fixes a roughness map will not fix your albedo - different maps need different values, and matching a whole material set by eye means tweaking each. The pack prints a console banner on every run, which is normal noise, not an error. If you need brightness and contrast and inversion in one place, look at the pack's fuller PBR Adjuster instead; this node is deliberately the simple one.