Curves is a graph that maps the original brightness of your pixels to new brightness values. Dragging a point up makes that tonal range brighter, and dragging it down makes it darker. Once you can read the graph, you can control contrast, exposure and color casts more precisely than with simple sliders.
Read the Graph
The horizontal axis shows input tones, from shadows on the left to highlights on the right. The vertical axis shows output tones. A straight diagonal line means no change.
- Lower left area: shadows.
- Middle area: midtones.
- Upper right area: highlights.
- Steeper line segments increase contrast, and flatter segments reduce it.
Always apply Curves as an adjustment layer from the Layer menu or the Adjustments panel. That keeps the edit non-destructive and lets you mask it later.
Build an S-Curve for Contrast
- Add a Curves adjustment layer.
- Click the middle of the line to add an anchor point and leave it in place.
- Click a quarter of the way up from the lower left and drag it down slightly to deepen shadows.
- Click three quarters of the way along the upper part and drag it up slightly to lift highlights.
- Compare with the original by toggling the layer visibility.
Keep moves small. A few points of movement often look better than a dramatic curve, and heavy curves can cause banding or harsh edges.
Control Color with Individual Channels
Switch the menu from RGB to Red, Green or Blue to edit color. Pulling a channel up adds that color to the tonal range, and pulling it down adds the opposite.
| Channel | Drag up adds | Drag down adds |
|---|---|---|
| Red | Red | Cyan |
| Green | Green | Magenta |
| Blue | Blue | Yellow |
To neutralize a color cast, use the gray point eyedropper on something that should be neutral, or lower the dominant channel in the affected range. For a warm look in highlights and cool tone in shadows, nudge red up in the highlights and blue up in the shadows slightly.
Use Masks and Blend Modes
- Layer mask: use a soft brush to confine the curve to a subject or a region, such as a dark foreground.
- Luminosity blend mode: set the layer to Luminosity so contrast changes do not shift color saturation.
- Color blend mode: use it for color-only curve edits that leave brightness unchanged.
- Targeted adjustment tool: click the hand icon, then drag on the image to add a point for the tone you touched.
FAQ
Is Curves better than Levels?
Curves offers more control because you can edit many points along the tonal range, while Levels adjusts black, white and midtone only. Levels is faster for quick fixes.
Why do my colors look too vivid after an S-curve?
Contrast curves in RGB also boost saturation. Change the layer blend mode to Luminosity to keep color levels steady.
The Short Version
Use Curves on an adjustment layer, make small moves, and watch the graph slope for contrast. Edit single channels for color, and combine masks and blend modes to keep each change precise.
