Colour Grade
Colour starts at exposure and ends at the viewer’s display. In between are transfer functions, colour spaces and two different jobs: correction (making the shot look right) and grading (making it look intentional).
- log recording
- LUTs
- colour correction
- grading
- scopes
- HDR
- Rec.709
What this section answers
- Why does log look grey?
- What does a LUT do and where should I use it?
- What is the difference between Rec.709 and HDR?
- What do the waveform and the vectorscope show?
Articles and tools
Quick reference
| parameter | SDR (BT.709 / BT.1886) | HDR (BT.2100) |
|---|---|---|
| primaries | BT.709 | BT.2020 |
| bit depth | 8 or 10 bit | 10 or 12 bit |
| transfer function | BT.1886 gamma (2.4) at the display | PQ or HLG |
| reference white | 100 cd/m² (BT.2035) | 203 cd/m² (HDR reference white) |
| reference display | black < 0.01 cd/m² | peak ≥ 1,000 cd/m², black ≤ 0.005 cd/m² |
Terms
- Log encoding log recording
- A logarithmic transfer function that squeezes the sensor’s wide dynamic range into the signal. The picture looks flat and needs a transform or grading. More
- LUT look-up table
- A table that maps each input colour to an output colour. A technical LUT converts between colour spaces; a creative LUT creates a look.
- Rec.709 BT.709
- The ITU-R recommendation for HDTV: colour primaries, resolutions and transfer parameters. The standard target for SDR output. More
- HDR high dynamic range
- Video with brighter highlights and a wider range of tones. For television it is defined by ITU-R BT.2100 through the PQ and HLG curves.
- PQ Perceptual Quantizer
- An absolute HDR curve (SMPTE ST 2084, ITU-R BT.2100) that encodes luminance up to 10,000 cd/m².
- HLG Hybrid Log-Gamma
- A relative HDR curve from ITU-R BT.2100 designed with compatibility with older displays in mind; widespread in broadcasting.
- Waveform monitor
- A scope that shows the luminance (or the RGB channels) of the picture from left to right. The basic tool for checking exposure.
- Vectorscope
- A circular scope that shows hue (angle) and saturation (distance from the centre). It helps you find colour casts and check skin tones.
- Chroma subsampling
- Notation such as 4:4:4, 4:2:2, 4:2:0: how much colour information is stored compared with luminance. Less colour = a smaller file and a worse key.
- Bit depth
- The number of levels per channel: 8 bits = 256, 10 bits = 1,024, 12 bits = 4,096. Greater depth reduces the risk of banding when grading.
In preparation
Topics we are working on. They are not published yet — we would rather have fewer pages, but verified ones.
- Scopes: waveform, parade and vectorscope in practice
- Colour correction vs. grading: the order of operations
- Colour management (ACES and in-application management)
- Monitor calibration: what you can do at home and what you can’t
- Matching shots from different cameras
Sources for the tables
Checked .