Adjust a tone curve to change contrast, lift shadows, hold highlights, or grade color through separate red, green, and blue channels. A curve is a map: each input value from 0 to 255 is sent to a new output value.
Tone curve basics
The curve graph reads from left to right:
- left: shadows and black values
- middle: midtones
- right: highlights and white values
The diagonal line means no change. Move part of the curve up to brighten that tonal range. Move it down to darken that range.
Click the graph to add a point. Drag points to reshape the curve. Double-click an interior point to remove it. Keep the curve smooth unless a hard, stylized break is intentional.
S-curves, lifted blacks, and highlight control
A small S-curve is the common contrast move: lower the shadow side slightly and raise the highlight side slightly. It adds separation without changing every tone by the same amount.
Lift the lower-left part of the curve for a faded or matte black point. Flatten the upper-right part when skies, white clothing, or product highlights are too harsh.
Sharp bends can create banding, especially in gradients and skies. If the image gets brittle, reduce the point movement or lower Mix.
RGB and color curves
Use the RGB curve first for contrast and exposure shape. It changes red, green, and blue together, so it behaves like a master tone curve.
Use Red, Green, and Blue curves for color work. Raising a channel adds that channel in the selected tonal range. Lowering it removes that channel and moves the image toward its opposite color.
Examples:
- raise Blue in shadows for cooler dark areas
- raise Red in highlights for warmer light areas
- lower Green slightly to reduce a green cast
Small channel moves are usually enough. Turn on Preserve luma when channel curves change brightness more than intended.
Mix and Preserve luma
Mix blends the curved result with the original image. 100% applies the full curve. 60% to 90% often keeps a strong curve usable without rebuilding it.
Preserve luma tries to keep brightness stable while color channels change. Use it for color grading and cast correction. Leave it off when the goal is a direct channel curve that can also change brightness.
Curves vs levels
Use Levels when the fix is mostly black point, white point, and midtone gamma. Use Curves when one part of the tonal range needs its own shape, such as lifted shadows with protected highlights, a precise S-curve, or separate color curves for shadows and highlights.
How the curve is applied
The editor builds lookup tables for the master RGB curve and each color channel. Each pixel passes through the RGB table, then the channel tables, then optional luma preservation, then the Mix blend. Preview uses a capped size for responsiveness; download renders the original dimensions.