The subject of HDR (high dynamic range) has become almost ubiquitous in any discussion of production or post-production, especially given that many TVs now claim to display HDR, but some confusion remains about what it is and how it might affect a particular project. It’s more than just brighter pictures – the image is crisper, clearer, more colorful and has more apparent sharpness. It more closely matches the dynamic range that can be seen by the human eye, which can reach 14 stops. Standard dynamic range is between six and ten stops, but HDR opens us up to seeing around 13 stops. Today’s digital cinema cameras (ARRI ALEXA family, Sony Venice, etc.) can capture between 11 and 15 stops, and film also has more than enough dynamic range. Until HDR displays, display technology was limiting the dynamic range that could be seen. Now HDR displays are available that can both increase the luminance levels of shadows, mid-tones, and highlights, while also retaining a solid black level. Unlike, 4K vs. HD, when most people see HDR for the first time, they notice a definite improvement.
There are a few HDR formats out there now. Dolby is a pioneer, introducing Dolby Vision™ a few years ago for both the home and for theatrical release. Dolby Vision™ isn’t just about HDR though – it uses dynamic metadata (scene by scene information) to ensure that content creators’ creative intent is delivered to the consumer no matter if they are watching in the cinema, at home on a television or a mobile device. It provides a variable peak brightness, depending on the capability of the display. In the cinema, Dolby Vision™ increases the contrast range from 2000:1 for DCI to around 1 million:1. Streaming services such as Netflix support Dolby Vision™ with popular shows like Altered Carbon, Birdbox and Black Mirror available to view.
HDR10 is an open source format introduced prior to Dolby Vision™. Unlike Dolby Vision™, there is no dynamic metadata involved, so the brightness doesn’t vary based on the capability of the display. Every HDR television supports HDR10, whereas Dolby Vision™ requires a license. Dolby Vision™ is also brighter, supporting up to 10,000 nits peak brightness. The two more recent formats are HDR10+ and Hybrid Log Gamma (HLG). HDR10+ has some of the same features as Dolby Vision™, dynamic metadata for example, but is an open standard and requires no licensing fee. Unlike Dolby Vision™, which is 12 bit, HDR10+ is only 10 bit (like HDR10). In April 2017 Samsung announced that it was partnering with Amazon Prime Video to support HDR10+. Amazon already has shows like The Marvelous Mrs. Maisel, The Man in the High Castle and The Grand Tour showing in HDR10+, with two shows (Tom Clancy’s Jack Ryan for example) available in both HDR10+ and Dolby Vision™. Finally, HLG was co-developed by the BBC and NHK and is royalty-free. Unlike the other HDR formats, it was developed for live broadcast. There is probably room for both Dolby Vision™ and HDR10+ to become the standards, but for a while, there will be televisions supporting legacy formats too.
The plethora of formats is more of an issue for post-production and distribution, but HDR delivery must be considered from on-set onwards. Monitoring on-set is a challenge, partly because until now HDR monitors have been prohibitively expensive and also because the viewing environment on-set is not optimal. However, shooting a well exposed negative - avoiding under and overexposure to prevent clipping or high levels of noise in the final image - remains the most important factor no matter the final delivery. Cinematographers may make subtle changes - David Mullen ASC, cinematographer on The Marvelous Mrs. Maisel, now in production on its third season, points out that he might knock down a bright window or light near actors in the frame, because it could be distracting in HDR – but really nothing should be that different from the pre-HDR world.
One question that often comes up in post-production for HDR is whether the HDR or SDR version should be graded first. Ideally, the HDR should be the master grade, and then the SDR should be a trim pass. Knowing your distribution channel is critical. If we use Netflix as an example, they require a Dolby Vision™ VDM (video display master). Mastering for Dolby Vision™ requires a color grading tool that is Dolby Vision compatible (Filmlight’s Baselight, BMD’s DaVinci Resolve are two examples) and an HDR reference grade mastering monitor that meets the Dolby Vision minimum specifications. The delivery to Netflix is a single-source IMF master which contains the HDR master, along with the “trim pass” metadata to derive SDR streams. When you stream a Netflix show to your home, Dolby Vision-certified TVs handshake with the streaming service and deliver the best-looking image possible, based on the capabilities of that specific TV model.
There’s bound to be a lot of new HDR displays for professional use at NAB this year, at lower prices than before, which means that HDR displays will be more practical to have in a near set and editorial environment. HDR, whether it’s HDR10, HLG, HDR10+ or Dolby Vision™ will make the pictures on consumer displays (cinema, home or mobile) brighter and more colorful. And perhaps more importantly, the dynamic metadata of HDR10+ and Dolby Vision™ can ensure that the artistic intent of the creator gets transmitted through to the home. That’s a big step forward and one that PIX fully embraces because we are committed to building tools that communicate creative intent.
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