---
title: "Color Grading Curves: RGB, Luma and Hue | colorgrade.video"
description: "Color grading curves explained: S-curves, the luma curve vs the RGB curve, per-channel curves, and Hue vs Hue, Hue vs Sat and Hue vs Luma for skies and foliage."
url: https://colorgrade.video/color-grading-tutorial/curves
---

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3. Curves

Chapter 5 of 13 · Intermediate · 8 min read

# Curves in Color Grading

A curve is the most flexible control in a grade. The sliders in **Adjust** and the wheels each change the picture in one fixed shape; a curve lets you draw the shape yourself, adding contrast in exactly the range you want, cooling only the deepest shadows or leaving one tone untouched while the rest moves.

The studio’s **Curves** panel has two families. The **Custom** curves remap level, either for all three channels together, for luma alone or for red, green and blue separately. The hue curves select by colour instead: **Hue vs Hue**, **Hue vs Sat**, **Hue vs Luma**, **Luma vs Sat** and **Sat vs Sat** change one range of colours and leave the rest. This chapter covers both, with real uses on landscape-sky, a landscape with blue sky and greenery, and ends with the **HSL** tab, the quicker cousin of the hue curves.

Video guide

## Color Grading Curves: Luma vs RGB S-Curve and Hue vs Sat Sky

Duration:  0:44 

Your browser can't play this video. [Download the MP4](https://colorgrade.video/media/videos/color-grading-curves-hue-vs-sat/video.mp4) or read the[full transcript](https://colorgrade.video/videos/color-grading-curves-hue-vs-sat).

Chapters

1. [ Play from  0:00 RGB vs Luma S-curve ](https://colorgrade.video/videos/color-grading-curves-hue-vs-sat#t=0)
2. [ Play from  0:16 A deeper sky ](https://colorgrade.video/videos/color-grading-curves-hue-vs-sat#t=16)
3. [ Play from  0:29 Foliage and shadows ](https://colorgrade.video/videos/color-grading-curves-hue-vs-sat#t=29)
4. [ Play from  0:43 Try it yourself ](https://colorgrade.video/videos/color-grading-curves-hue-vs-sat#t=43)

English captions [Watch page and full transcript ](https://colorgrade.video/videos/color-grading-curves-hue-vs-sat) 

## Key takeaways

* A curve maps input (along the bottom) to output (up the side): points above the diagonal raise those tones, points below lower them.
* The **RGB** curve adds saturation along with contrast; the **Luma** curve changes level and keeps colour.
* Channel curves on **Red**, **Green** and **Blue** fix or create a cast at chosen levels only.
* Hue curves select by colour: shift a hue, scale its saturation or change its level without a mask.
* Use two anchor points either side of a hue point to keep a hue-curve change narrow.

## In this chapter

1. [ 1. How a curve works ](#how-curves-work)
2. [ 2. S-curves: contrast you can shape ](#s-curves)
3. [ 3. The luma curve vs the RGB curve ](#luma-vs-rgb)
4. [ 4. Red, Green and Blue channel curves ](#channel-curves)
5. [ 5. Hue curves: change one colour without a mask ](#hue-curves)
6. [ 6. The HSL tab, and when to use a qualifier instead ](#hsl-tab)
7. [ 7. Grade a landscape with curves ](#try-it)

## How a curve works

A **Custom** curve plots input level along the bottom, from black on the left to white on the right, and output level up the side. With no change it is a straight diagonal: every input comes out as itself. Click to add a point, drag it to move, double-click a point to remove it, and **Reset curve** returns to the diagonal. The black and white end points can be moved too, which sets the black and white points directly.

Read a curve by its slope as well as its position. Where the curve is steeper than the diagonal, tones in that range are spread apart and gain contrast; where it is flatter, they are squeezed together and lose it. That is why every curve is a trade: contrast gained in one range is taken from another.

The studio draws smooth, shape-preserving curves that never overshoot between points. In practice that means a point can’t make a neighbouring range bend the wrong way, and curves never fold back on themselves, the cause of the posterised, solarised look some editors produce when points are placed close together.

## S-curves: contrast you can shape

The classic contrast curve is an S. Pull a point at about a quarter of the way along down a little and push a point at about three-quarters up a little: the midtones get steeper, so they gain contrast, while the two ends flatten so shadows and the lightest tones roll gently into black and white instead of clipping. Add a third point in the middle, on the diagonal, to stop mid grey moving.

* Place the steepest part of the S where the subject’s tones are. On a face lit at about 50%, centre the S there and the face gains shape.
* An inverse S, flatter in the middle, softens a harsh, contrasty shot.
* Raising the black end point of the curve gives the lifted, matte black of a [film look](https://colorgrade.video/film-look); lowering the white end point dulls the top end for a vintage feel.

The **Contrast** slider applies a fixed S around mid grey; a curve lets you choose where the S sits and how far each half bends. For the tonal groundwork that comes before it, see [contrast and tonal range](https://colorgrade.video/color-grading-tutorial/contrast-and-tonal-range).

[ ![The Curves panel on the Custom tab with Luma selected and a gentle S-curve: the quarter-tone point lowered slightly, the three-quarter point raised, the end points unchanged, beside the landscape with stronger contrast.](https://colorgrade.video/guides/color-grading-tutorial/curves/luma-s-curve.webp)  (enlarge image) ](https://colorgrade.video/guides/color-grading-tutorial/curves/luma-s-curve.webp) 

A gentle S-curve on **Luma** adds contrast without louder colour.

## The luma curve vs the RGB curve

The channel buttons above the **Custom** curve are **Luma**, **RGB**, **Red**, **Green** and **Blue**. The first two look alike but behave differently, and the difference is one of the most useful things to know about curves.

The **RGB** curve applies the same curve to red, green and blue. For a grey pixel that only changes level. For a coloured pixel, whose three channels sit at different levels, a steep part of the curve pushes the channels further apart, so an S-curve on **RGB** adds saturation along with contrast, and can nudge hues slightly too. On landscape-sky, an RGB S-curve makes the grass and sky noticeably more vivid.

The **Luma** curve changes only luma (Y, the weighted brightness). The studio works out how much the curve moves each pixel’s luma and adds that same amount to all three channels, which keeps the hue and the colour difference intact. The same S-curve on **Luma** adds the contrast without the extra saturation.

__Which curve to use__
| You want                                     | Use                | Why                            |
| -------------------------------------------- | ------------------ | ------------------------------ |
| Punchy contrast with richer colour           | RGB                | Saturation rises with contrast |
| Contrast without louder colour, e.g. on skin | Luma               | Colour difference is kept      |
| A cast fixed only in the shadows or top end  | Red, Green or Blue | One channel at chosen levels   |
| A split tone without wheels                  | Blue (and Red)     | Opposite moves at each end     |

[ ![Side by side compare of the landscape: the original on the left, and on the right the same frame with an S-curve on the RGB curve, showing stronger contrast and deeper greens and blues, above a vectorscope trace that reaches further from the centre.](https://colorgrade.video/guides/color-grading-tutorial/curves/rgb-s-curve-saturation.webp)  (enlarge image) ](https://colorgrade.video/guides/color-grading-tutorial/curves/rgb-s-curve-saturation.webp) 

An S-curve on **RGB** adds saturation as well as contrast: watch the **Vectorscope**.

## Red, Green and Blue channel curves

The **Red**, **Green** and **Blue** curves change one channel at chosen levels, which makes them both a correction tool and a styling tool. Watch the **Parade** while you work: each curve moves exactly one of its three traces.

* Fix a cast that lives only in the shadows: if the bottom of the blue trace sits high, add a point low on the **Blue** curve and pull it down, with an anchor in the middle to protect the rest.
* Cool shadows, warm top end: raise the low part of the **Blue** curve and lower its upper part. The result is a split tone similar to cool **Lift** and warm **Gain**, but you choose exactly where the crossover falls.
* Cross-processed looks bend the channels in opposite directions, for example an S on **Red** and **Green** and an inverse S on **Blue**. The [creative looks chapter](https://colorgrade.video/color-grading-tutorial/creative-looks) builds looks like this.

For broad balance the wheels are quicker; reach for channel curves when a cast changes across the tonal range. The [colour wheels chapter](https://colorgrade.video/color-grading-tutorial/color-wheels) compares the two approaches.

## Hue curves: change one colour without a mask

The hue curves select pixels by colour. On **Hue vs Hue**, **Hue vs Sat** and **Hue vs Luma**, the bottom axis runs through the hues, red, yellow, green, cyan, blue, magenta and back to red, and the flat line across the middle means no change. Raise or lower a point and only pixels of that hue respond. **Pick colour** adds a point at the hue you click on the picture, so you don’t have to guess where the sky’s blue sits on the axis.

Near-neutral pixels have no reliable hue, so the studio fades hue shifts and saturation boosts out as colours approach grey: clouds, white shirts and grey concrete don’t pick up stray colour.

__The five hue curves__
| Curve       | Selects by | Changes          | Real use                            |
| ----------- | ---------- | ---------------- | ----------------------------------- |
| Hue vs Hue  | Hue        | Hue, up to ±180° | Turn yellowish foliage greener      |
| Hue vs Sat  | Hue        | Saturation, 0-2x | Deepen the sky, calm a neon sign    |
| Hue vs Luma | Hue        | Level, ±2 stops  | Richer, deeper blue sky             |
| Luma vs Sat | Level      | Saturation       | Desaturate the deepest shadows      |
| Sat vs Sat  | Saturation | Saturation       | Lift muted colours, calm vivid ones |

### Make the sky deeper

On **Hue vs Sat**, use **Pick colour** on the sky, then raise that point slightly. Add anchor points on the flat line either side, around cyan and around purple, so the change stays inside the blues. Then on **Hue vs Luma**, lower the blue a touch. Together they give the deeper sky that a polariser would: richer colour and a little less level, rather than the cartoon blue that saturation alone produces.

[ ![The Hue vs Sat curve with a raised point in the blues and flat anchor points around cyan and purple, beside the landscape whose sky is a deeper blue while the grass is unchanged.](https://colorgrade.video/guides/color-grading-tutorial/curves/hue-vs-sat-sky.webp)  (enlarge image) ](https://colorgrade.video/guides/color-grading-tutorial/curves/hue-vs-sat-sky.webp) 

**Hue vs Sat** raised at the sky’s blue, with anchors either side.

### Fix green foliage

Grass and leaves often record as yellow-green, which reads as dry or unhealthy. On **Hue vs Hue**, put a point on the yellow-green and raise it slightly: those hues turn a few degrees towards green, while true yellows and the sky stay put. For greens that are too loud, lower the same range on **Hue vs Sat** instead.

[ ![The Hue vs Hue curve with a small raised point on yellow-green, turning the landscape’s yellowish grass a few degrees towards green while the sky and yellows stay the same.](https://colorgrade.video/guides/color-grading-tutorial/curves/hue-vs-hue-foliage.webp)  (enlarge image) ](https://colorgrade.video/guides/color-grading-tutorial/curves/hue-vs-hue-foliage.webp) 

**Hue vs Hue** turns yellow-green foliage towards green.

### Calm a neon sign, quiet the shadows

A magenta sign or a saturated LED strip can pull the eye away from the subject. A narrow dip on **Hue vs Sat** at its hue calms it without touching skin. **Luma vs Sat** works on level instead of hue: lowering its left end desaturates the deepest shadows, which hides colour noise and gives cleaner blacks, and lowering its right end gives the gentle desaturation of the lightest tones that film shows. **Sat vs Sat** scales saturation by how saturated a colour already is, so raising its left half brings life to muted colours without pushing vivid ones over the edge.

## The HSL tab, and when to use a qualifier instead

**HSL** offers the same idea with fixed bands: **Red**, **Orange**, **Yellow**, **Green**, **Aqua**, **Blue**, **Purple** and **Magenta**, each with **Hue**, **Saturation** and **Luminance** sliders. It is faster than drawing hue curves, and the bands cover the common jobs: **Blue** for skies, **Green** and **Yellow** for foliage, **Orange** for skin. **Keep only this colour** turns everything else monochrome for a colour-splash effect, and **Reset HSL** clears all bands. To recolour an object outright, the [change a colour in a video](https://colorgrade.video/change-color-in-video) page shows the quickest route.

Choose hue curves when the colour you want falls between two bands or needs a narrower range; choose **HSL** for speed. And when the colour you want to change is shared by something you want to keep, a blue shirt under a blue sky, or skin and a wooden table, no hue-based control can tell them apart. That is the job of a qualifier and a power window on their own layer, covered in [secondary colour correction](https://colorgrade.video/color-grading-tutorial/secondary-color-correction).

## Grade a landscape with curves

Add contrast with a luma S-curve, deepen the sky with Hue vs Sat and Hue vs Luma, and fix the greens with Hue vs Hue.

1. 1  
### Open the clip with the scopes
Choose **Open video or photo**, switch to **Pro**, open **Curves** on the **Custom** tab, and show **Waveform** and **Vectorscope**.
2. 2  
### Add contrast on Luma
Select **Luma** and draw a gentle S: a point at a quarter lowered slightly, a point at three-quarters raised slightly.
3. 3  
### Deepen the sky
Open **Hue vs Sat**, use **Pick colour** on the sky and raise that point a little, with anchor points either side. On **Hue vs Luma**, lower the blue slightly.
4. 4  
### Fix the greens
On **Hue vs Hue**, add a point on the yellow-green of the foliage and raise it slightly so it turns towards green.
5. 5  
### Quiet the shadows and compare
On **Luma vs Sat**, lower the left end of the curve to desaturate the deepest shadows, then set **Compare** to **Split**.

## Curves: questions

### What is an S-curve in color grading?

A curve with the lower part pulled down and the upper part pushed up, so it looks like a gentle S. It steepens the midtones, adding contrast there, while rolling the shadows and the lightest tones smoothly towards black and white. It is the most common way to add contrast with a curve.

### What is the difference between the luma curve and the RGB curve?

The **RGB** curve applies the same curve to red, green and blue, so adding contrast also spreads coloured pixels’ channels apart and raises saturation. The **Luma** curve changes only luma and keeps each pixel’s colour difference, so it adds contrast without making colours louder.

### What does Hue vs Sat do?

It changes saturation by hue. Raise the curve at one hue and only colours of that hue become more saturated; lower it and they become calmer. It is the standard way to deepen a blue sky or tone down one over-saturated colour without touching the rest.

### How do I make the sky more blue in a video?

On **Hue vs Sat**, raise the curve at the sky’s blue (use **Pick colour** on the sky), with anchors either side to keep the change narrow, then lower the same hue slightly on **Hue vs Luma** for depth. The **Blue** band in **HSL** is a quicker alternative.

### Should I use hue curves or HSL?

**HSL** is quicker and covers most jobs with eight fixed colour bands. Hue curves are more precise: you choose the exact hue and how wide the change is, which helps when a colour falls between two bands. If the colour is shared by something you want to keep, use a qualifier instead.

### Why do curves make my colours more saturated?

Contrast added to red, green and blue together stretches the differences between the channels of every coloured pixel, which raises saturation. Use the **Luma** curve for contrast without that side effect, or lower **Saturation** slightly after an **RGB** curve.

[ ← Previous: chapter 4 Colour wheels ](https://colorgrade.video/color-grading-tutorial/color-wheels) [ Next: chapter 6 → Secondary correction ](https://colorgrade.video/color-grading-tutorial/secondary-color-correction) 

## Keep going

* [ Colour wheels What each colour wheel does in plain maths, how the master ring and puck differ, when to use log wheels, and what the primary bars add. ](https://colorgrade.video/color-grading-tutorial/color-wheels)
* [ Secondary correction Isolate one colour or one area of the frame with a qualifier or a power window, check the matte, and grade that part alone. ](https://colorgrade.video/color-grading-tutorial/secondary-color-correction)
* [ Contrast and tonal range Set black and white points, place mid grey, and shape contrast without clipping either end, using the waveform and false colour. ](https://colorgrade.video/color-grading-tutorial/contrast-and-tonal-range)
* [ Change a color in a video Swing one hue band round to a new colour with the HSL controls. ](https://colorgrade.video/change-color-in-video)
* [ Change video saturation online Saturation and Vibrance for the whole picture, HSL for one colour at a time. ](https://colorgrade.video/video-saturation)

All 13 chapters 
1. [ 1\. Video scopes ](https://colorgrade.video/color-grading-tutorial/video-scopes)  · Basics
2. [ 2\. Contrast and tonal range ](https://colorgrade.video/color-grading-tutorial/contrast-and-tonal-range)  · Basics
3. [ 3\. White balance ](https://colorgrade.video/color-grading-tutorial/white-balance)  · Basics
4. [ 4\. Colour wheels ](https://colorgrade.video/color-grading-tutorial/color-wheels)  · Intermediate
5. [ 5\. Curves ](https://colorgrade.video/color-grading-tutorial/curves)  · Intermediate
6. [ 6\. Secondary correction ](https://colorgrade.video/color-grading-tutorial/secondary-color-correction)  · Intermediate
7. [ 7\. Skin tones ](https://colorgrade.video/color-grading-tutorial/skin-tones)  · Intermediate
8. [ 8\. Log footage and LUTs ](https://colorgrade.video/color-grading-tutorial/log-footage-and-luts)  · Advanced
9. [ 9\. Creative looks ](https://colorgrade.video/color-grading-tutorial/creative-looks)  · Advanced
10. [ 10\. Shot matching ](https://colorgrade.video/color-grading-tutorial/shot-matching)  · Advanced
11. [ 11\. Delivery and export ](https://colorgrade.video/color-grading-tutorial/delivery)  · Advanced
12. [ 12\. Grading workflow ](https://colorgrade.video/color-grading-tutorial/workflow)  · Intermediate
13. [ 13\. Common mistakes ](https://colorgrade.video/color-grading-tutorial/mistakes)  · Basics