Shima Brightness/Contrast

Brightness and contrast adjustments are the condiments of image work - a little goes a long way, and everyone needs them at some point. Shima Brightness/Contrast does the job with one slider at a time and no fuss. It's not a grading suite, and it makes no claim to be one. What it is: a dead-simple, instant, batch-friendly tweak that sits nicely at the tail of a workflow, right before you save.

How it works

Read the mechanism before you assume anything, because the "contrast" here is not what a colorist means by contrast. In the source:

• brightness does image + strength, clamped to 0–1. Additive. Positive brightens, negative darkens.
• contrast does image * strength, clamped to 0–1. That's a straight multiply - a gain. Strength 1.0 is identity (no change), 0.5 halves every channel, 0 crushes everything to black.

A true contrast curve pivots around mid-gray, keeping your midtones anchored while stretching highlights and shadows. This node doesn't do that; it just scales. The practical consequence: keep contrast values near 1.0 and treat it as a "gain" knob, not a "punch" knob. Negative contrast is a trap - the multiply goes negative, everything clips to black, and you'll think the node is broken.

The inputs that matter

• image - required IMAGE input.
• mode - brightness or contrast. One mode per node; if you want both, use two of these nodes in series.
• strength - −1 to 1, step 0.01. For brightness that's a sensible additive range. For contrast, remember the identity point is 1.0, not 0.
• enabled - the pass-through toggle. Turn it off and the image comes out untouched. Handy when you're A/B testing whether the grade is helping at all.

Single IMAGE output, so it chains anywhere.

When you'd use it

This is a "quick pass" node: darken an overexposed render, lift a muddy one, then hand off to a save node or a proper post-processing chain. In Shima's ecosystem it slots into a workflow as a one-off adjustment between the sampler output and MultiSaver. If you find yourself needing real tonal control - curves, lifts, per-channel balance - you're better served by a proper post-processing pack; this is deliberately simple.

Installing it

Part of the Shima pack. ComfyUI Manager → search Shima, or:

cd ComfyUI/custom_nodes
git clone https://github.com/KDB-USJP/shima_wf.git Shima

Restart. First launch auto-installs Python deps and the pack's two companion repos (ComfyUI-Impact-Pack, cg-use-everywhere).

Common issues

• Contrast set to 0.5 looks like the image got darker, not "lower contrast." That's the multiply mechanism doing exactly what it says. Lowering toward 1.0 from the top is the usable direction.
• Negative strength crushes to black. Expected with a multiply; don't do it.
• "Why does nothing change?" - enabled is off, or strength is sitting at the identity point (0 for brightness, 1.0 for contrast).

Honestly? If you need to darken or lighten a render in a hurry, this is fine. If you need to grade it, look elsewhere. Knowing which is which is half the battle.