Tone Curve

A graph that maps input brightness to output brightness. The core tool for fine-grained regional adjustments and building a signature look — things sliders can't quite do.

Reading the graph

output
↑ 1.0  ┌────────┐
       │       ╱
       │      ╱   ← how you bend this line is everything
       │     ╱
  0.5  │    ╱
       │   ╱
       │  ╱
       │ ╱
  0.0  └─────────→ input
       0    0.5   1.0
       (dark)   (bright)

• X-axis (input): brightness in the original image
• Y-axis (output): brightness after editing
• Default straight line: "exactly as captured." Bend it and tones change.

Pull a point upward → the input brightness at that x position becomes brighter. Pull down → darker.

Thinking in four regions

Lightroom's tone curve splits into named zones:

0 ──── 25 ──── 50 ──── 75 ──── 100
 Blacks   Shadows   Lights   Highlights
   ↑        ↑        ↑          ↑
 black-end  dark    bright    white-end
            mids    mids

Almost the same as the slider set Blacks/Shadows/Highlights/Whites, but with the curve you choose where the boundaries fall.

The S-curve — the one you reach for often

output
↑ 1.0  ┌──────╱─┐
       │     ╱ ←─── brights pushed brighter
       │   ╱
  0.5  │ ╱   ← midtones unchanged
       │╱
       ╱   ←─── darks pushed darker
  0.0  └─────────→ input

• Lower the dark end, raise the bright end → contrast up.
• This is the move you reach for when you say "make it pop."

🔴 The S-curve's side effect — saturation

S-curves don't only raise contrast — they raise color saturation as well. As tones intensify, reds and blues intensify with them.

If you don't want that:

• Pull saturation back slightly in HSL/Color Mixer, or
• Use the Parametric Curve (4 region sliders) for a softer touch instead of a Point Curve, or
• Use the Lab/HSL Curve to touch only luminance (Lightroom Classic option)

The faded look (lifted blacks)

output
↑ 1.0  ┌────────┐
       │      ╱
       │    ╱
       │  ╱
  0.2  │╱     ←─── black starting point lifted from 0 to 0.2
  0.0  └─────────→ input

Lifting the black output value from 0 to ~0.15–0.25 turns black into a muted gray for that filmic feel. Signature look of early Instagram filters.

RGB channel curves — the entrance to color grading

The technique you've used now and then. The most powerful tool here.

Pulling per-channel curves lets you inject color into specific tonal regions:

Teal & Orange (the most common cinematic look):

• Blue curve, dark end ↑ (blue/cyan in shadows)
• Red curve, bright end ↑ (orange in highlights)

Difference from the Color Grading panel

Lightroom's newer Color Grading panel (formerly Split Toning) gives you a GUI for part of what RGB curves can do. Faster, but RGB curves have higher precision.

Quick work = Color Grading; precision work = RGB tone curves.

Practical tips

• Start with the Parametric Curve (4 region sliders) until it feels comfortable, then move to the Point Curve.
• Don't place more than 3–5 points. More than that gets unnatural and risks banding.
• For RGB channel curves, only nudge the ends slightly. Even 0.05 makes a clear difference.

Related

• color-and-dynamic-range — Parent note
• dynamic-range — Compared to the slider four
• hsl-and-color-mixer