Curves

Curves remap brightness: the horizontal axis is the input, from black on the left to white on the right, and the vertical axis is the output. A straight diagonal line changes nothing. Bend it and you change how each level of brightness comes out.

Editing a curve

• Click on the curve to add a point, then drag it.
• Double-click a point to remove it.
• Pick a channel with the buttons above the curve: M (master) changes brightness, and R, G and B change one colour channel each.

The histogram drawn behind the curve shows where your image's tones actually are, so you can see which part of the curve affects the most pixels.

Common shapes

• S-curve (Master): pull a point in the shadows down and a point in the highlights up. This adds contrast through the midtones without clipping the ends, which is why most looks use one.
• Lifted blacks (Master): drag the bottom-left end point straight up. Nothing is pure black any more, which reads as matte or filmic.
• Split tone (Blue): raise the shadow end of the blue curve and lower its highlight end. Shadows go blue, highlights go yellow.

Channel curves

On a single channel, raising the curve adds that colour and lowering it adds its opposite: less red is more cyan, less green is more magenta, less blue is more yellow. Channel curves can fix a colour cast in just the shadows or just the highlights, which white balance can't.

Hue curves

Switch the panel from RGB to Hue for four more curves, the ones DaVinci Resolve calls by the same names. Here the horizontal axis is a colour (or, on Lum vs Sat, a brightness), and the dashed line through the middle means no change: drag a point above it to add, below it to take away.

• Hue vs Hue: shifts one colour toward its neighbours, up to 60° either way. Turn a green sky teal, or pull orange skin away from red.
• Hue vs Sat: saturates or mutes one colour. Mute the greens in foliage without touching skin.
• Hue vs Lum: brightens or darkens one colour, up to a stop either way. Darken a blue sky.
• Lum vs Sat: saturation by brightness. Pull it down at the left for clean, less noisy shadows, or at the right for softer highlights.

Each hue curve starts with six points at red, yellow, green, cyan, blue and magenta, so dragging one colour only bends the curve between its neighbours. Click to add a point (it lands on the curve, so nothing changes until you drag it), or press Pick and click the photo to add a point at that colour's hue. Flatten resets the curve that's open.

Greys and near-greys are left alone by the three hue curves, since a grey pixel's hue is mostly noise. Hue curves are free, and they're baked into an exported LUT like the rest of the grade.