Curves in Photography — An Interactive Tone Curve Editor
The tone curve is a core tool for contrast and color. This page includes a working curve editor — drag points and see the effect on a photo in real time, with no installs or uploads.
Tone Curve(RGB)
drag · tap to add · tap × to removePresets
Click to apply to the RGB channel.
Before / After
landscape-sunrays.jpg · press B to see full before/after · drag the handle (or double-click) to reset.
Choose an image
Six varied samples — or upload your own. Files are processed locally and never uploaded.
Privacy-first: your photo stays on your device — no server upload.
1. Pick a sample or upload a photo.
2. Drag a point to reshape the curve.
3. Tap (or double-click) the line to add a point; select a point and tap × to remove it.
4. Switch R / G / B to color-grade, then export PNG or JPG.
What is a curves adjustment?
A curves adjustment is a brightness-and-color remapping tool found in Lightroom, Photoshop, Capture One, and virtually every raw editor. Unlike a simple brightness slider that shifts the whole image equally, a curve lets you change specific tonal regions — deep shadows, midtones, and highlights — independently.
The curve plots input on the horizontal axis and output on the vertical axis. When the line is a straight diagonal, input equals output and nothing changes. When you bend the line, you tell the editor: "take this brightness level and make it brighter or darker."
How to read a tone curve
The bottom-left corner is pure black (0); the top-right corner is pure white (255). The gray bars behind the line are the histogram — a chart of how many pixels sit at each brightness level. The left of the histogram is your shadows, the middle your midtones, and the right your highlights.
Where the curve sits above the diagonal, that tonal range gets brighter. Where it sits below, it gets darker. A steeper section of curve increases contrast in that range; a flatter section reduces it.
The S-curve: add contrast
The most famous curve is the S-curve. Pull a point in the lower third down to deepen shadows, and push a point in the upper third up to brighten highlights. The steeper middle adds midtone contrast and gives the image "punch."
Try it: in the editor above, click the S-Curve (Contrast) preset on a high-dynamic-range image like "Sun through clouds."
Lifting shadows & crushing blacks
Drag the bottom-left point upward and pure black becomes soft gray — that's "lifting blacks." Drag the top-right point downward and pure white becomes gray — that's "crushing whites." Together they produce the popular faded, film-like look.
Try it: apply Matte Fade, then slowly drag the black point up and watch the shadows melt away.
Color grading with individual RGB channels
Switch from the master RGB curve to the R, G, or B tab to edit a single channel. Lifting the blue curve in the shadows while lowering it in the highlights creates the classic teal-and-orange split. Boosting red in the midtones warms skin without touching overall brightness.
Try it: open the portrait sample, switch to R, and raise the middle of the curve to warm the skin tones.
Understanding the histogram
The histogram is a bar chart of brightness. A tall peak on the left means lots of dark pixels (a low-key image); a tall peak on the right means lots of bright pixels. When a curve flattens one end, the histogram bunches up there — watch the bars compress as you lift blacks or crush whites.
Gaps at the far left or right usually mean no true black or true white. A quick contrast S-curve spreads the histogram out, filling both ends with detail.
Curves vs. levels
Levels only let you set black, white, and midtone points — three anchors. Curves let you place as many points as you want and reshape any tonal region, plus edit individual color channels. Once you understand the curve, you'll rarely need levels again.
Common curves mistakes to avoid
- Over-bending: extreme curves clip detail and create harsh banding. Keep transitions smooth.
- Ignoring the histogram: a curve that looks dramatic on screen may be crushing shadows — watch the bars.
- Editing color when you only wanted contrast: make sure you're on the RGB tab for brightness-only changes.
Frequently asked questions
What does a curves adjustment do in photography?
A curves adjustment remaps the brightness of an image. The horizontal axis is the input value (original brightness from black to white) and the vertical axis is the output value (the new brightness). Reshaping the diagonal line lets you brighten shadows, darken highlights, add contrast, or shift colors channel by channel.
What is an S-curve?
An S-curve is the classic contrast move: pull the lower third of the line down to deepen shadows and push the upper third up to brighten highlights. The result is a gentle S shape that adds punch and separation without clipping.
How do I lift blacks for a matte/faded look?
Raise the bottom-left (black) point of the curve upward. Pure black now maps to a dark gray, removing harsh shadows and creating a soft, film-like fade. Lowering the top-right (white) point completes the matte look by softening highlights.
What is the difference between RGB and per-channel curves?
The RGB (master) curve affects red, green, and blue equally — it changes only brightness/contrast. The individual R, G, and B curves let you shift color balance and grade the image, because boosting the blue curve in shadows while reducing it in highlights creates a warm-cool split.
Do I need to upload my photos to use this tool?
No. Everything runs in your browser. Uploaded images are read locally with the File API and are never sent to any server, which keeps your photos private.