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HDR COLOUR GRADING FOR UK FILM AND TV: HLG, PQ AND BROADCAST DELIVERY.

Industry guide · Colour

By Fitzrovia Post · 14 October 2026

What BT.2100 means for UK post

Recommendation ITU-R BT.2100 specifies image parameter values for high dynamic range television for production and international programme exchange. It defines two HDR methodologies: Hybrid Log-Gamma (HLG) and Perceptual Quantisation (PQ). (ITU-R BT.2100; Channel 4 / DPP file delivery specification)

The Channel 4 / DPP technical specification for AS-11 file delivery — agreed by DPP broadcasters including the BBC, Channel 4, Channel 5, ITV, Sky, STV and TG4 — summarises the practical difference: HLG offers a degree of compatibility with legacy displays by more closely matching earlier television transfer curves, while PQ achieves a very wide brightness range for a given bit depth using a non-linear transfer function tuned to the human visual system. (Channel 4 / DPP file delivery specification)

For UHD programmes delivered under that shared DPP framework, colour space is ITU-R BT.2100, and image dynamic-range parameters detailed in BT.2100 must be agreed with the broadcaster before delivery. SMPTE ST 2036-1 cannot be used for high dynamic range images. (Channel 4 / DPP file delivery specification)

Consult the broadcaster before HDR production

Guidance for HDR programmes sits in the DPP HDR Supplement, but the AS-11 file specification is explicit: the broadcaster must be consulted before an HDR production commences. The same rule appears in the BBC’s technical delivery standards for AS-11 files. (Channel 4 / DPP file delivery specification; BBC technical delivery standards (Scotland commissioning PDF); Channel 4 Delivery)

That early conversation usually locks:

Leaving those decisions until after the grade is how projects discover that a streaming PQ or Dolby Vision-style master is not yet a UK broadcast deliverable.

HLG for commissions, PQ for many acquisitions

Under the shared DPP wording used by Channel 4 and the BBC’s AS-11 standards:

EBU Recommendation R 154, which sets parameters for UHD/HDR programmes exchanged as files, likewise recommends ITU-R BT.2100 Hybrid Log-Gamma as the transfer function for baseline UHD file exchange (SDR transfer functions are not allowed under that recommendation). (EBU R 154)

Grading display brightness

The DPP / Channel 4 and BBC AS-11 specifications state that HDR programmes should normally be graded on displays with a maximum brightness of between 1000 and 2000 cd/m². (Channel 4 / DPP file delivery specification; BBC technical delivery standards)

Report ITU-R BT.2408 (operational practices for HDR television production) adds practical monitoring context for HLG: HDR monitors are necessary for critical monitoring such as colour grading, camera shading and programme/preview outputs, while the compatible nature of HLG allows SDR monitors in non-critical areas. For HLG reference displays, a nominal peak luminance of 1000 cd/m² is identified in BT.2100 and has been found to work well in typical production environments; nominal peak signal level on the production monitor should be set to a comfortable level for the viewing environment and need not equal the monitor’s absolute peak capability. (ITU-R BT.2408)

Graphics levels: 75 IRE and 203 nits

For HLG productions, the DPP / Channel 4 specification recommends that the reference level of graphics should be 75 IRE. That leaves headroom for specular highlights and supports comfortable viewing when HLG content is shown on both HDR and SDR displays. The same document notes that 75 IRE is equivalent to 203 cd/m² on a 1000 cd/m² reference display, or 343 cd/m² on a 2000 cd/m² reference display. (Channel 4 / DPP file delivery specification)

ITU-R BT.2408 aligns with that practice. It defines HDR Reference White (also diffuse white and Graphics White) as the nominal signal level from a 100% reflectance white card, resulting in a nominal luminance of 203 cd/m² on a PQ display or on an HLG display with a nominal peak luminance of 1000 cd/m². On the signal scale that is 75% HLG or 58% PQ. SDR graphics should be mapped into HDR at that Graphics White level so overlays do not appear too bright and make the underlying video look dull. (ITU-R BT.2408; EBU R 154)

EBU R 154 repeats the same exposure guidance table for exchange masters: HDR Reference White / diffuse white / graphics white at 75% HLG, with 18% grey at 38% HLG. (EBU R 154)

File delivery: AS-11, UHD and IMF

For day-to-day UK Network television, the BBC requires programmes to be delivered as AS-11 DPP files, with full editorial and technical QC before delivery. Channel 4 publishes its current DPP/Channel 4 technical specification for file delivery through its Programme Management / Delivery pages. (BBC technical requirements; Channel 4 Delivery)

For UHD, the shared DPP AS-11 document describes AS-11 DPP X1 (“MXF Program Contribution – DPP UHD”) as the UHD file format, with HDR type (and any special delivery arrangements) discussed in advance with the broadcaster. The BBC’s AS-11 standards document additionally states that UHD programmes for iPlayer are required as SMPTE TSP2121-1 IMF packages, with an AS-11 HD version also delivered via the standard portal. (Channel 4 / DPP file delivery specification; BBC technical delivery standards)

EBU R 154 notes that the BBC has adopted IMF using Application DPP (ProRes) for post-produced UHD television content, and points producers to the BBC technical-requirements page for the live delivery specification. (EBU R 154; BBC technical requirements)

Always confirm the exact package, codec and metadata profile with the commissioning broadcaster — Channel 4’s published DPP file document also notes Channel 4-specific constraints (including historical limits on accepting UHD material), so the live portal document is the source of truth for each commission. (Channel 4 / DPP file delivery specification)

Streaming PQ / Dolby Vision masters vs UK broadcast HLG

Many international and streaming pipelines still master in PQ (sometimes with Dolby Vision metadata layered on a PQ base). That is not the same thing as a UK DPP commissioned HLG deliverable. The DPP specs allow either BT.2100 method in principle, but say commissioned programmes must normally be HLG, while acquisitions are the usual home of PQ — with conversion via the BT.2100 annex when a change of method is required. (Channel 4 / DPP file delivery specification)

ITU-R BT.2408 and related ITU reports describe operational conversion between PQ and HLG (including the need for a conversion rather than a naive transcode, because the systems render differently on displays of different peak luminance). Plan for an agreed HLG broadcast master (and any SDR down-map) rather than assuming a streaming PQ or Dolby Vision package will pass UK broadcast QC unchanged. (ITU-R BT.2408)

What producers and colourists should confirm early

Fitzrovia Post provides picture post, colour finishing support and related audio post from studios in central London. To talk through HDR delivery for your next commission, send us a project brief.

FAQ What is the difference between HLG and PQ? Both are HDR methods in ITU-R BT.2100. HLG is designed with closer compatibility to legacy television curves; PQ uses a perceptual quantiser for a very wide brightness range. UK DPP specs normally expect commissioned programmes as HLG and treat many acquisitions (especially movies) as PQ.

Do I need broadcaster approval before starting an HDR grade? Yes. DPP / Channel 4 and BBC AS-11 delivery documents state that the broadcaster must be consulted before an HDR production commences.

What brightness should the grading display be? HDR programmes should normally be graded on displays with a maximum brightness between 1000 and 2000 cd/m², per the shared DPP wording.

Where should HLG graphics sit? At a reference level of 75 IRE (75% HLG / Graphics White). That equals 203 cd/m² on a 1000 cd/m² reference display, or 343 cd/m² on a 2000 cd/m² reference display.

Is Dolby Vision required for UK broadcast? No claim in the DPP AS-11 specs requires Dolby Vision for UK commissioned delivery. Commissions are normally HLG; PQ (sometimes used in streaming masters, including pipelines that also carry Dolby Vision metadata) is more typical of acquisitions and needs agreed conversion when HLG broadcast delivery is required.

How are BBC UHD programmes packaged? BBC Network TV programmes are delivered as AS-11 DPP files. For UHD iPlayer, the BBC’s AS-11 standards document requires SMPTE TSP2121-1 IMF packages (with an AS-11 HD version also delivered). Confirm the live BBC technical-requirements page for the current UHD IMF detail.

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