Short answer
The usual method is to grade the HDR version first on a reference monitor and derive the SDR version from it. Software analyses each shot of the HDR master and maps it down to a 100 cd/m² target; the colourist then reviews that mapping shot by shot and adjusts it with a limited set of trim controls. The trims travel as metadata with the HDR master, so one file can produce the SDR version and renderings for televisions of different brightness.
Going down is easier than going up. An HDR master holds highlight detail and saturated bright colour that an SDR version has to compress or discard; an SDR master has already discarded them and cannot supply them to an HDR version. The colourist of House of the Dragon put it in those terms: it is much easier to get the HDR right and then go down to SDR than the reverse. Dolby's guide builds its whole procedure on that order and says the tools exist to maintain the look and intent of the HDR master in what is derived from it.
In Dolby Vision the first step after grading is analysis. The software examines every frame of a shot and records three values for the shot as a whole: its darkest, its average and its brightest level. With the mastering display's own characteristics, those values let a mapping algorithm decide how to fit that shot into a smaller range. The guide requires the timeline to be cut accurately into shots first, because an analysis that straddles a cut produces brightness that flickers or jumps on playback, and it forbids pasting one shot's values across a whole reel.
The automatic mapping is a starting point. With the target set to a 100 cd/m² Rec. 709 display, the colourist steps through every shot and, where the mapping misreads the intent, adjusts it with trim controls. The older version of the system offers six, among them lift, gamma, gain and saturation, which the guide notes act on the tone-mapping curve and not as the ordinary grading controls of the same names. The newer version offers twenty-one. The guide requires the 100 cd/m² pass whether or not an SDR deliverable is wanted, because other targets are interpolated from it.
HDR10 carries one description for the whole programme: the mastering display and the content's maximum and average light levels. A television uses it to choose one mapping, which a dark scene and a bright scene must share. Dynamic metadata changes per shot. HLG takes a third route and carries none: its signal describes relative scene light, and ITU-R BT.2100 has each display apply a system gamma that depends on its own peak, 1.2 at 1,000 cd/m² and lower on dimmer screens. Separately graded masters remain an option; Roma was delivered as distinct SDR and HDR files.
The master is graded on a reference display under reference conditions. BT.2100 specifies that display as reaching at least 1,000 cd/m² with black at or below 0.005 cd/m². A home television is dimmer at the top and brighter at the bottom, sits in a lit room and applies its own processing, so what the viewer sees is the master re-rendered by the set, guided by metadata where the format has it. Web pages add another layer of uncertainty: a browser may tone-map HDR video for an SDR desktop in a way no one graded.
Nothing on this site is a calibrated reference. A web page is shown by a browser that may or may not colour-manage, on a screen of unknown white point, brightness and response, so no still or swatch here can reproduce a graded image.
| Level | Scope | What it carries |
|---|---|---|
| 0 | Whole programme | The mastering display and the picture's aspect ratio |
| 1 | Per shot | Analysis: the shot's minimum, mid and maximum levels. Not editable |
| 2 | Per shot, per target | Creative trims in the earlier content-mapping version: six controls |
| 3 | Per shot | Offsets applied to the level 1 analysis |
| 5 | Per shot | Aspect ratio where a shot differs from the programme's |
| 6 | Whole programme | Optional HDR10 static values: maximum content and frame-average light level |
| 8 | Per shot, per target | Creative trims in the later content-mapping version: twenty-one controls |
| 9 | Per shot | The primaries of the source content |
| Luminance | What it is | PQ signal | 10-bit narrow-range code |
|---|---|---|---|
| 0.005 cd/m² | BT.2100 reference display black | 1.5% | 77 |
| 1 cd/m² | Deep shadow | 15.0% | 195 |
| 100 cd/m² | SDR reference white | 50.8% | 509 |
| 203 cd/m² | HDR reference white (BT.2408) | 58.1% | 573 |
| 600 cd/m² | A mid-range HDR television | 69.6% | 674 |
| 1,000 cd/m² | Common mastering peak | 75.2% | 723 |
| 4,000 cd/m² | High mastering peak | 90.3% | 855 |
| 10,000 cd/m² | Top of the PQ range | 100.0% | 940 |
| Display peak | System gamma |
|---|---|
| 400 cd/m² | 1.03 |
| 600 cd/m² | 1.11 |
| 1,000 cd/m² | 1.20 |
| 2,000 cd/m² | 1.33 |
| 4,000 cd/m² | 1.45 |
| Format | Publisher | Edition | What it is | Limit of this record |
|---|---|---|---|---|
| ITU-R BT.2100 (PQ and HLG) | ITU-R | BT.2100-3 (02/2025), in force | Image parameters for HDR television. It specifies two systems: PQ, whose signal maps to absolute display light, and HLG, whose signal encodes relative scene light and keeps a degree of compatibility with older displays. It also sets a reference viewing environment. | HLG is scene-referred where PQ is display-referred; the single label here is for PQ. |
| SMPTE ST 2084 | SMPTE | ST 2084:2014 | The standard that first defined the PQ transfer function for HDR mastering displays, later adopted in BT.2100. | Only the publication record was confirmed; the curve is described from BT.2100. |
| HDR10 | Consumer Technology Association | HDR10 Media Profile, announced 27 August 2015 | An open HDR profile: PQ, 10 bits, BT.2020 primaries and static metadata describing the mastering display and the content's light levels for the whole programme. | Summarised from a reference work because the association's definition could not be read. Static metadata cannot describe a change from scene to scene. |
| Dolby Vision | Dolby Laboratories | Grading guide version 4.0 (16 December 2019) | A proprietary HDR format built on a PQ master plus dynamic metadata: a per-shot analysis of the image's darkest, average and brightest levels, and optional trims a colourist sets for particular target displays. | The owner's 2019 guide; two content-mapping versions exist and their trims differ. |
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
Dolby's guide sets out the Dolby Vision process as creating the HDR master, creating per-shot analysis metadata, optionally applying creative trim metadata, and creating deliverables, and requires the HDR grade to be mapped to and checked against a 100-nit Rec. 709 target for every shot.
Caveat: Version 4.0 of the guide, dated December 2019.
Source: Dolby Vision Color Grading Best Practices Guide, version 4.0
StandardStrong evidence
ITU-R BT.2100-3 specifies a reference HDR display with peak luminance of at least 1,000 cd/m² and black level of at most 0.005 cd/m², viewed with a neutral D65 surround at 5 cd/m².
StandardStrong evidence
ITU-R BT.2100-3 gives the HLG system gamma as 1.2 at a nominal display peak of 1,000 cd/m² and provides a formula adjusting it for displays of other peak luminance.
FactModerate evidence
The HDR10 profile combines the PQ transfer function, 10-bit depth and BT.2020 primaries with static metadata only, which stays the same for the whole programme.
Caveat: Summarised from a reference work; the Consumer Technology Association's own definition could not be read.
Source: HDR10
FactModerate evidence
House of the Dragon was graded HDR-first at 1,000 nits with the SDR version derived from that grade, and Roma was delivered as separate SDR and HDR masters.
Source: Crafting Legacy for House of the Dragon (Matt Mulcahey, American Cinematographer, 2 December 2022); Roma: Memories of Mexico (Mark Dillon, American Cinematographer, 7 January 2019)
Colourwise analysisStrong evidence
On the PQ curve, SDR reference white at 100 cd/m² sits at about 51 per cent of the signal range and 1,000 cd/m² at about 75 per cent, so the top quarter of the signal is reserved for luminances most masters never use.
Based on: Calculated by Colourwise from the BT.2100 reference PQ function; see the table on this page.
Reviewed 6 October 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.