HDR — High Dynamic Range
Definition
HDR (high dynamic range) video extends the range between the darkest and brightest parts of the image beyond that of SDR, and is used with the wide colour gamut of Rec.2020. ITU-R BT.2100 defines two transfer functions: PQ (perceptual quantizer, SMPTE ST 2084), which encodes absolute luminance up to 10,000 cd/m² (nits), and HLG (hybrid log-gamma, developed by the BBC and NHK, ARIB STD-B67), which is relative and compatible with SDR displays. HDR10 uses PQ with static metadata (SMPTE ST 2086, MaxCLL and MaxFALL). HDR10+ (SMPTE ST 2094-40) and Dolby Vision (SMPTE ST 2094-10) add dynamic metadata that adapts tone mapping scene by scene. Displaying HDR requires an HDR source, a chain that passes the signalling and metadata, and an HDR-capable display. HDCP 2.2 is required only for protected content, such as commercial 4K HDR streaming.
In the field
HDR content sent into a chain set for SDR looks flat and washed out, and SDR content interpreted as HDR looks dark or oversaturated. Before the event, the transfer function (EOTF, electro-optical transfer function) and the colour space set on the source, the processor and the display are checked against the content format.
Related lessons
Sources
- ITU-R BT.2100-3 : fonctions de transfert PQ (jusqu'à 10 000 cd/m²) et HLG pour la télévision HDR · itu.int
- Wikipédia, HDR10 : PQ (SMPTE ST 2084), métadonnées statiques SMPTE ST 2086, MaxCLL et MaxFALL (pointeur secondaire) · en.wikipedia.org
- HDR10+ Technologies, HDR10+ System Whitepaper : métadonnées dynamiques normalisées dans SMPTE ST 2094-40 · hdr10plus.org
- Wikipédia, Dolby Vision : métadonnées dynamiques SMPTE ST 2094-10 (pointeur secondaire) · en.wikipedia.org
- Wikipédia, Hybrid log–gamma : HLG mis au point par la BBC et la NHK, ARIB STD-B67 (pointeur secondaire) · en.wikipedia.org