# Color Primaries

Canonical URL: https://encode.wiki/reference/colorimetry/primaries/
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Color primaries say which exact red, green and blue the RGB values refer to, plus the white point. Together they define the gamut: the triangle of colors the signal can express. ffprobe reports them as `color_primaries`.

Primaries are a separate property from the [transfer function](/reference/colorimetry/transfer/) and the [matrix](/reference/colorimetry/matrix/), but each video system uses a fixed set, so in practice the three tags usually agree: BT.709 everywhere for HD, BT.2020 everywhere for UHD and HDR.

## Code points

| Code | FFmpeg name | System | Where you see it |
| --- | --- | --- | --- |
| 1 | `bt709` | BT.709; also the sRGB primaries | HD video, web video, sRGB images |
| 2 | `unknown` | Not specified | Untagged files; the player guesses |
| 4 | `bt470m` | BT.470 System M | Obsolete NTSC |
| 5 | `bt470bg` | BT.470 System B/G, BT.601 625-line | PAL/SECAM SD and DVD |
| 6 | `smpte170m` | SMPTE 170M, BT.601 525-line | NTSC SD and DVD |
| 7 | `smpte240m` | SMPTE 240M; same as 6 | Obsolete |
| 8 | `film` | Generic film, illuminant C | Rare |
| 9 | `bt2020` | BT.2020 / BT.2100 | UHD SDR, HDR10, HLG, Dolby Vision |
| 10 | `smpte428` | CIE 1931 XYZ (SMPTE ST 428-1) | Digital cinema distribution masters |
| 11 | `smpte431` | DCI-P3, DCI white point | Cinema |
| 12 | `smpte432` | P3 with D65 white (P3-D65) | Display P3 content, Apple devices |
| 22 | `ebu3213` | EBU Tech 3213-E / JEDEC P22 | Rare |

The chromaticities you need most often, for example when writing HDR mastering metadata:

| Primaries | Red (x, y) | Green (x, y) | Blue (x, y) | White (x, y) |
| --- | --- | --- | --- | --- |
| BT.709 / sRGB | 0.640, 0.330 | 0.300, 0.600 | 0.150, 0.060 | D65: 0.3127, 0.3290 |
| BT.601 525 (SMPTE 170M) | 0.630, 0.340 | 0.310, 0.595 | 0.155, 0.070 | D65 |
| BT.2020 | 0.708, 0.292 | 0.170, 0.797 | 0.131, 0.046 | D65 |
| P3 (DCI and D65) | 0.680, 0.320 | 0.265, 0.690 | 0.150, 0.060 | D65, or DCI 0.314, 0.351 |

SVT-AV1 calls code 6 `bt601` and code 7 `smpte240`; VapourSynth uses `170m`, `2020`, `st432-1`, and so on. The number is the same everywhere.

## Practical notes

**Untagged SD.** NTSC and PAL primaries differ slightly from BT.709. Players guess when the tag is missing — mpv picks BT.709 for anything 1280 wide or over 576 high, PAL for 576 lines and NTSC for 480 or 486 — so tag SD encodes with the source system or convert them when upscaling (see [the color guide](/guides/preserve-color-and-hdr/#sd-bt601-to-hd-bt709)).

**BT.2020 is a container, not the content's real gamut.** Most HDR is graded on a P3-D65 monitor and delivered in BT.2020. The stream is tagged `bt2020`; the mastering-display metadata records P3. Don't tag such a stream `smpte432` because the grade was P3 — the samples are BT.2020 values.

**BT.2020 does not mean HDR.** UHD SDR also uses BT.2020 primaries. Whether a stream is HDR is decided by the [transfer](/reference/colorimetry/transfer/) (`smpte2084` or `arib-std-b67`).

**P3 variants.** DCI-P3 and P3-D65 share primaries but differ in white point. Apple's Display P3 is P3-D65 primaries with the sRGB transfer, so it is tagged `smpte432` plus `iec61966-2-1`.

**Retagging does not change the gamut.** Tagging BT.709 pixels as `bt2020` makes every color look oversaturated; tagging BT.2020 pixels as `bt709` makes them look dull. Going from a wide gamut to a narrow one is a real conversion that has to decide what to do with colors outside the smaller triangle — use `zscale`, `libplacebo` or VapourSynth `resize` with explicit input and output primaries, and tone-map at the same time if the source is HDR (see [tone mapping](/hdr/#tone-map-hdr-to-sdr)).