Levels

Four tone curves: one for the whole image and one each for red, green and blue. Drag a curve up to brighten those tones or down to darken them – an S adds contrast, a lifted toe fades the blacks. The histogram behind it shows where your pixels sit.

The color channels are how you tint: pull blue down in the shadows for warm darks, lift it in the highlights for cool brights. Double-tap a channel on the rail to reset it.

Behind the percentage dot, Strength scales whatever shape you drew. White Point and Black Point set where the photo’s range ends; raise Black Point and the darkest tones go fully black, the quick fix for a flat, hazy file. Preserve Hue stops a steep curve from shifting colors.

On black and white stocks only the global curve is available.