Contrast

A flat image is the most common complaint after a generation - models love to render things gray and washed. The naive fix is a contrast slider, and the naive slider is why so many people over-crank it into crunchy black-and-white messes. LF_Contrast is the LF Nodes version that gives you control instead of a sledgehammer, and the two knobs that matter are the midpoint and the local-contrast toggle.

• contrast_strength - −1 to 1, default 0.25. Note the tooltip's framing: 1.0 is no change, below 1 reduces contrast, above 1 increases it. So 0.25 sits slightly on the increase side of "normal," and to actually boost contrast you go toward 1 (or you read it as: negatives soften, positives punch).
• midpoint - 0 to 1, default 0.5. This is the tonal anchor the contrast pivots around. Leave it at 0.5 for a general punch-up; move it up or down to aim the adjustment at the highlights or the shadows.
• localized_contrast (optional) - when on, applies contrast "locally to edges and textures" rather than globally. That's the texture-preserving setting: it gives you the snap of higher contrast on fine detail without flattening the overall tonal range.

How it fits

Standard LF filter behavior: accepts a batch or single tensor, returns image and image_list, and renders a KUL_COMPARE before/after widget on the node. Pipeline placement: right after a sampler to fix flatness, or before an upscaler to give it more defined edges to work with.

The realistic workflow: your render comes out muddy → contrast 0.4–0.5, localized_contrast on, midpoint 0.5 → the image gains depth and texture snap without turning into a poster. Compared to the pack's LF_Clarity (which does midtone contrast plus sharpening), this is the pure tonal control; clarity is for when you want the crispness too.

Installing it

Standard LF Nodes:

cd ComfyUI/custom_nodes
git clone https://github.com/lucafoscili/comfyui-lf

or ComfyUI Manager → LF Nodes → install → restart. No dependencies, no models. The pack is the frozen legacy repo (the author moved active development to lf-nodes), so this node is stable and unchanged.

Where people get burned

• The 1.0-means-no-change convention trips everyone once. A value of 0.25 is not "25% of max punch" - it's a small bump past normal. Don't multiply by 4 trying to reach max; just watch the compare widget.
• Over-cranking with localized_contrast off flattens the image - global contrast up too high kills your shadow and highlight separation. If it looks posterized, back off and turn localized on.
• Stacking this on top of LF_Clarity double-applies midtone work. Use one or the other unless you really know what you're doing.

For fixing the "why is everything gray" problem with actual control, this is the node.