What it does
Precise tone and color control. Drag points on a curve to brighten, darken, or add contrast, overall or per channel.
The graph rewards learning to read it. The horizontal axis is the image as it is, shadows on the left, highlights on the right; the vertical axis is the image as it will be. Wherever the curve runs steeper than the original diagonal, tones are being spread apart, which the eye reads as contrast and detail. Wherever it runs flatter, tones are being squeezed together and detail compresses. That one rule decodes every curve you will ever see: a grade is just a decision about which parts of the range deserve steepness and which can afford to give it up.
The famous shapes follow directly. The S-curve steepens the midtones, where faces and subjects live, by flattening the extremes a little, which is why it adds punch without clipping anything. Its inverse flattens the middle for the low-contrast, log-like look. Raising the bottom endpoint lifts the deepest blacks into a matte haze; a gentle rolloff at the top protects highlights. Every named film preset, every one-click look, decomposes into a handful of these moves stacked together.
Per-channel curves are where correction turns into grading. A curve on the blue channel that rises in the shadows and dips in the highlights pushes shadows cool and highlights warm, the backbone of the cinematic split-tone, all in one gesture. In Modulate the composite curve applies first with the per-channel curves refining on top, the points interpolate through a spline that stays monotonic so the curve remains a legitimate tone map however far a point is dragged, and the result runs identically on every frame of video.
Signature looks
Filmic S
Midtones steepened, extremes cushioned. The all-purpose contrast move that makes footage look finished rather than filtered.
Faded log
Blacks lifted and the whole curve relaxed toward flat. The washed, pre-grade look that reads as expensive restraint.
Split tone
Opposing per-channel moves that cool the shadows and warm the highlights. The two-color grade built from curves alone.
Try it on your own footage
This effect runs live in the Modulate editor, with layers, effect chains, masks, and keyframes. Free, no signup, nothing to install.
Common questions
What does a curves adjustment do?
It remaps tones through a user-drawn graph: every possible input brightness is assigned an output brightness by the height of the curve at that point. Dragging the curve up brightens the tones under that region, dragging it down darkens them, and placing multiple points lets different parts of the range move in different directions at once, something single-slider tools cannot do.
How do you read a tone curve?
Shadows sit at the lower left, highlights at the upper right, and the diagonal means no change. Judge any segment by its slope: steeper than the diagonal means more contrast and more visible detail in those tones, flatter means less. A grade is a budget, since steepening one region always means flattening another, and the curve shows exactly where that trade is being made.
What is an S-curve?
The most common curves move: a point pulled down in the shadows and a point pulled up in the highlights, bending the line into a gentle S. It steepens the midtones, adding contrast where subjects usually live, while easing off in the deep shadows and bright highlights so nothing clips. It flatters almost any image, which is why it is the first move most colorists make.
What is the difference between curves and levels?
Levels adjusts the tonal range with fixed handles: endpoints and a midtone. Curves opens the whole response up, letting you place any number of points anywhere, so you can lift only the lower shadows or roll off only the top of the highlights, moves levels simply cannot express. The trade is precision for speed: levels answers in seconds, curves rewards a slower hand.
Can you use curves on video?
Yes. A tone curve is a per-pixel remap, so a grade drawn once holds identically across every frame with nothing to track. In Modulate the curves effect runs live on images and video in the browser, with composite and per-channel curves that update the picture as you drag.
Related effects
Levels adjustment
Adjusts brightness and contrast by setting new black, white, and midtone points.
Gradient map
Recolors the image by mapping its dark and light areas onto a gradient you design.
Posterize effect
Collapses smooth gradients into a few flat tonal bands for a screen-printed, cel-shaded look. Band per channel or by brightness, with a gamma bias to push the steps toward shadows or highlights.
Hue shift
Rotates every color around the color wheel, and can keep the colors cycling over time.