brightness contrast

The Brightness_Contrast_Ally node (displayed as "brightness contrast") is a tiny pre-save color tweaker: pick a mode, set a strength, adjust. It's one of the pack's three ports of "theAlly"'s nodes - the author folded them in because people kept struggling to install the originals - with an enabled switch added so you can leave the node in place and bypass it with a click instead of deleting it.

How it works - and the honest math

The node's mode picks between two one-line operations, both applied to the raw pixel values:

• brightness: adds strength to every pixel (clamped to 0–1). Positive brightens, negative darkens.
• contrast: multiplies every pixel by strength (clamped to 0–1).

Here's the part worth understanding before you use it: "contrast" here is really just multiply. It's not the pivot-around-mid-gray contrast curve you might expect from photo editing - at strength 1.0 nothing changes, and anything below 1.0 simply darkens the whole image toward black. So this mode can never add contrast the way a proper contrast slider does; it can only scale brightness down. For an actual contrast curve you'd want a proper color-grading node. Within its range, though, it's dead simple and predictable.

Inputs and outputs

• image (IMAGE, required) - the image to adjust.
• mode (enum: brightness or contrast) - which operation to apply.
• strength (FLOAT, default 0.5, range -1.0 to 1.0) - the amount. For brightness, -1.0 to 1.0 is the full dark-to-light range. For contrast, remember the multiply caveat above.
• enabled (BOOLEAN, default true) - off means pass-through.
• Output: IMAGE.

When you'd use it

Right before saving or previewing, the author's stated intent - fixing a slightly-too-dark render or knocking an image down to something softer before it hits a save node. It's a finishing knob, not a grading suite, and that's fine: sometimes you just need one slider.

Installing it

Same pack, same steps:

cd ComfyUI/custom_nodes
git clone https://github.com/aegis72/aegisflow_utility_nodes

Restart ComfyUI, or install "AegisFlow Utility Nodes" from ComfyUI Manager. No models, no heavy dependencies.

Where people get burned

Expecting "contrast" to behave like Photoshop's. It doesn't - see the math above. And because the operation is a straight per-pixel clip, pushed extremes will blow out highlights or crush shadows with no graceful rolloff. If you're after subtle tonal correction, use small strengths; if you need a real contrast curve, reach for a proper color node instead and keep this one for the quick knob.