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HDR Mastering

HDR is not a look or an export setting. It encodes brighter highlights and ties code values to measurable display luminance.

Three things change relative to an SDR master:

  • The transfer function. This is the curve that translates the numbers stored in a file into light on a screen. SDR and HDR use different curves, which is why an HDR file played as though it were SDR does not simply look dim. It looks wrong.
  • The container is wider. HDR encodes into a colour space large enough to hold more saturated colour than Rec.709 can describe. That is headroom, not an instruction to fill it.
  • Metadata travels with the picture, describing the display the grade was made on, so a television with different capabilities can adapt the image sensibly instead of guessing.

All three must be correct for predictable playback outside the grading room.

The standard: ITU-R BT.2100

BT.2100 is the recommendation that defines HDR television. Its parameters:1

Parameter Value
Primaries R (0.708, 0.292) · G (0.170, 0.797) · B (0.131, 0.046): the BT.2020 primaries
White point D65
Bit depth 10 or 12 bit
Transfer functions PQ (Perceptual Quantization) or HLG (Hybrid Log-Gamma)
Reference display peak ≥ 1,000 cd/m²: for small-area highlights, not full-screen white

BT.2100 defines a container gamut, not a requirement to grade to the BT.2020 primaries, and no display on the market reaches those primaries anyway. See BT.2020 is a container below.

PQ and HLG are not interchangeable

PQ (SMPTE ST 2084) is absolute: each code value maps to a luminance up to 10,000 cd/m². Use it for cinematic mastering and streaming.

HLG is relative and designed for live production and broadcast, with partial SDR compatibility.

For scripted streaming content, use PQ unless the delivery specification requires HLG.

Metadata

An HDR master is incomplete without metadata describing the display it was made on. This is a genuine change from SDR practice, where the mastering display was implied by the standard.

Standard Carries Kind
SMPTE ST 2086 Mastering display color volume: primaries, white point, min/max luminance Static
MaxCLL / MaxFALL Maximum content light level. Maximum frame-average light level Static
SMPTE ST 2094 Dynamic metadata for color volume transform, per-scene or per-frame Dynamic

ST 2086 describes the mastering display. MaxCLL and MaxFALL describe the content. Record both accurately. Incorrect values cause downstream tone-mapping errors that may not appear on the reference monitor.

Distribution formats

Format Metadata Notes
HDR10 Static (ST 2086 + MaxCLL/MaxFALL) The baseline. PQ, 10-bit, Rec.2020 container. Royalty-free.
HDR10+ Dynamic (ST 2094-40) Scene-by-scene metadata without a proprietary grading step.
Dolby Vision Dynamic (ST 2094-10) Adds an authored trim pass. Effectively mandatory for premium streaming delivery.

Netflix does not accept HDR10-only masters for originals. Plan its HDR delivery as Dolby Vision, with L1 analysis metadata covering every shot.

Dolby Vision changes the schedule. Grade the HDR master, then have the colorist author trims for lower-capability displays and SDR. This is a creative pass, not an export setting.2

The metadata comes in levels, and the three you will hear named are L1, L2 and L8.

L1 is generated analysis metadata. One L1Min/L1Mid/L1Max set describes each shot. It is not editable. Shot events must cover the timeline without gaps or overlaps. Dissolves, transitions, and long-play analysis may use per-frame events.

Build accurate shot boundaries from an EDL where possible. Boundaries that miss the picture cut can produce luminance shifts or flashing and commonly fail Dolby Vision QC.

The shot that swings from dark to bright

A single continuous shot that moves from a dark interior to a bright exterior is the classic problem case: one L1 set has to describe both ends, so the analysis lands between them and neither maps well. You cannot fix it by keyframing L1. Those values are generated, not editable.

Cut at the transition midpoint and add a dissolve across the cut. Each half receives separate analysis while the dissolve creates smooth per-frame metadata.

L2 and L8 are per-shot, per-target creative trims. L2 belongs to CM v2.9. L8 belongs to CM v4.0 and adds more controls. Confirm the required content-mapping version before booking the trim pass. Changing versions requires another creative pass.

Budget the trim pass

Budget the Dolby Vision trim and SDR review as creative work, not metadata export.

One master or two?

Choose before finishing whether SDR will be graded separately or derived from HDR trim metadata.

One master or two. The derived route runs through the trim metadata. A discrete SDR grade is a separate pass on the stage.

Requirements vary:

  • Netflix takes a single Dolby Vision master plus its sidecar XML and derives the SDR streams from the metadata. There is no separately graded SDR in the chain.
  • Sky requires the opposite: a separate Rec.709 grade where an HDR deliverable is commissioned, and states that it will not convert HDR to SDR itself.
  • Disney permits either, but requires that derived-versus-discrete be settled with mastering early in finishing.
  • Dolby requires the colourist to check the SDR Rec.709 100-nit mapping across the whole timeline whichever route you take, because that mapping is what SDR displays fall back to.3

Confirm whether "SDR master" means a derived file or a separate grade. The difference may be several days of stage time.

L2 and L8 trims are image-global. They provide no windows, keyers, or spatial secondaries. If the look depends on regional corrections, budget a separate SDR grade.

Netflix requires L1 but not L2 or L8. Complete a trim pass anyway to verify SDR rendering.

Mastering in practice

Grade in P3-D65. That is what almost every HDR master is actually made in, at a stated peak luminance: commonly 1,000 or 4,000 cd/m². You grade inside the volume your mastering display can genuinely measure and reproduce, not inside the container the file is encoded in.

The container is a separate question, and the delivery specification names it. Rec.2100/BT.2020 is the common case, but Netflix asks for a P3-D65 container, so read the schedule rather than assuming the wider one.

BT.2020 is a container

BT.2020 uses monochromatic primaries on the spectral locus.4 Real displays emit broader bands. Only laser systems approach full coverage. Treat BT.2020 as encoding headroom, not a grading target. Grade within the measured volume of the mastering display, usually P3-D65.

A typical deliverable set for a streaming feature:

  • HDR master: PQ, P3-D65 inside Rec.2100, 1,000 nit, with ST 2086 + MaxCLL/MaxFALL
  • Dolby Vision metadata: trims authored against that master
  • SDR master: Rec.709 / BT.1886, derived from the HDR grade with a colorist pass

Theatrical

Theatrical HDR is a separate presentation, not the home master, and it arrives two ways: brighter projection, and self-emissive LED walls.

Projected HDR includes Dolby Vision Cinema and HDR by Barco. Both exceed the 48 cd/m² DCI reference and require their own delivery specifications.

  • Dolby Vision Cinema uses dual-laser projection and dynamic per-scene metadata.
  • HDR by Barco uses Lightsteering to redirect light toward highlights.5

Direct-view LED displays replace projection with a self-emissive wall. DCI-certified HDR targets about 300 nits peak across the display. Examples include Samsung Onyx, Cinity LED, and LG Miraclass.6

Either way, a theatrical HDR pass is its own grade, and its own line item.

Consequences for visual effects

Plan HDR requirements with VFX before shot work:

  • Bit depth. The argument only strengthens for HDR: 10-bit log is not enough. 12-bit log is the floor for HDR finishing, 16-bit float preferable. See Camera Log.
  • Highlights are visible now. Specular detail, practical lights, and skies that clipped invisibly in a Rec.709 grade are plainly visible at 1,000 nits. Comps that "worked" in SDR reveal blown highlight rolloff, clipped CG speculars, and mismatched black points.
  • Review at the target. Use an HDR reference display rather than assuming Rec.709 review will translate.
  • Use exposure checks. Raise and lower exposure to compare artificial highlight clipping with the plate.

  1. ITU-R BT.2100-3 (February 2025): Table 2 (system colorimetry), Table 3 (reference viewing environment, whose Note 3c carries the small-area-highlight qualifier), and Table 9 (10- and 12-bit integer representation). ↩

  2. Dolby Vision Color Grading Best Practices Guide v4.0 and the Dolby Vision Professional Tools User Manual v4.0.0 cover trim workflow and the metadata levels in detail. ↩

  3. Netflix Partner Help Center, Dolby Vision HDR Mastering Guidelines. Sky's clause is in its Technical Specification for Delivery of Content to Sky. Disney's in its Dolby Vision Best Practices Guide. The SDR-check requirement in Dolby's Color Grading Best Practices Guide (v4.x). No standards body publishes a position on derived versus discrete SDR: it is a distributor-by-distributor question. ↩

  4. ITU-R BT.2020 (adopted by BT.2100 for HDR) defines the wide-gamut primaries as monochromatic single-wavelength points: red 630 nm, green 532 nm, blue 467 nm. ↩

  5. HDR by Barco and the LS4K projector. Launched at CinemaCon, April 2024. The contrast and gamut figures are Barco's. ↩

  6. DCI direct-view display specification and certification. The ~300-nit HDR figure and the product details are from manufacturer and integrator sources (GDC Technology, Samsung Onyx, LG Miraclass). ↩