HDR shootingIn Jan 2017 I presented a workshop “Shooting for HDR” with colourist Kevin Shaw, for the Guild of Television Cameramen, at Dolby's Soho screening room. We wanted to give people working in production a primer on what HDR is, and what they need to know about this exciting new development.
Watch the HDR workshop here.
Here are some points from my slides:
High Dynamic Range (HDR) is about a new generation of TVs capable of displaying significantly...
- More dynamic range
- More saturated colours
- More subtlety of colours
It's about screen technology catching up with the huge improvements already made in cameras: we shoot log with 14 stops dynamic range, but until now our TVs have been based around the REC709 standard: limited colour saturation, and limited dynamic range of around 6-7 stops.
Strictly speaking HDR standards only specify dynamic range, but “more colours” has been bundled with the improved screens. And the key word here is: SCREENS. We’ve been capturing HDR on digital cameras for 10 years, on film cameras for 50 years; only now can consumers buy TVs that can reproduce almost all of that range.
How important is HDR ?
High Dynamic Range is as important as the introduction of High Definition.
Won’t it be like 3D - nearly forgotten in 2 years?
No. It’s a markedly improved viewing experience requiring no bolt-on devices. Everyone gets it straight way. It’s here to stay.
There are three main flavours of HDR for tv screens:
|Dolby Vision||Proprietary. 12-bit. Scene-by-scene metadata.|
|HDR10||Non-proprietary. 10-bit. Static metadata. Ultra HD Blu-ray.|
|HLG||or Hybrid Log Gamma: Developed by BBC + NHK. 10-bit. No metadata. Uses existing production/transmission. Backward-compatible to HD TVs.|
Screen Brightness is measured in NITS = cd/m² = Candela per square metre.
- 100 nits = Rec709 = SDR: This dates back to the capability of the cathode ray tube. A reference monitor in a rec709 grade will be set to 100 nits brightness.
- 200 - 400 nits are our home TVs, computers, smartphones. Their rec709 pictures are usually stretched up to 200 nits peak.
- 500 nits = OLED HDR TVs. 2016 Apple screens are 500 nits.
- 1,000 nits: LCD HDR TVs. Also the max. brightness of Sony’s grading monitor, the BVM X300. HDR Blu-Ray DVDs are mastered to 1,000 nits peak.
- 4,000 nits is max. luminance of Dolby's Pulsar reference monitor, the brightest in existence.
- 10,000 nits is the theoretical maximum brightness of HDR; as defined by the Perceptual Quantizer curve (PQ Curve) developed by Dolby, and in 2015 standardised by SMPTE in ST.2084.
More subtlety of colours: HDR screens are 10-bit, up from SDR's 8-bit; you see less colour-banding, eg in skies. (Dolby Vision is 12-bit). 8-bit is 16 million individual colours, 10-bit is a billion colours.
More colours: nearly DCI-P3 colour-space in today's HDR TVs, expanded from REC709.
View samples of my work, or download my CV.