Building a new colour paradigm

Working with high dynamic range brings fresh challenges in post production
4K, Colour grading, Deluxe Encore, Deluxe’s Company 3, MyTherapy, UHD, Analysis, Content production

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Production of 4K content may no longer present an issue but premium UHD programming will likely require treatment for high dynamic range (HDR) in order to display a fuller range of colour and contrast. Indeed, Netflix, Amazon and YouTube are primed to stream HDR later this year and are commissioning content accordingly.

As the industry gets to grips with the technology it must also understand the implications for SDR - or standard dynamic range. This is the range of colour and contrast that is able to be displayed now in accordance to specification Rec.709 and which the majority of viewers will be watching until such time as sufficient HDR-enabled TV sets penetrate the market.

Working to Rec.2020 contained in a new set of UHD specifications, images are so enhanced they are said to reveal far more naturalistic colours. At the same time, there are warnings from colourists pioneering HDR workflows to resist the temptation to show off the new effect unless it fits the content.

The workflow doesn’t change much for acquisition or when it comes to hardware and file handling. HDR is a purely a display technology, so only that end needs to evolve but there are some gaps – notably on-set reference monitors and more monitoring options than the Sony BVM-X300 which seems to be the only one of its kind on the market.

Leading colourists pioneering HDR talk about their experiences to date.

Marco Polo, Dado Valentic, Mytherapy

Hired to work as colour scientist for season 2 of ten part Netflix drama Marco Polo, Dado Valentic, founder and chief colourist at Soho’s Mytherapy, developed a pipeline that enabled cinematographer Vanja Cernjul to precisely control the HDR on location in Hungary, Slovakia and Malaysia.

Rushes were shot on Sony F55, the same as season 1. “In order to acquire HDR you don’t need to change the camera or way of shooting provided you have sufficient bit depth to extract the dynamic range from the raw material,” Valentic advises.

With no on-set monitors yet available for displaying HDR, Valentic devised a means for Cernjul to know he was capturing enough information from an SDR display. It’s a proprietary process which meant Cernjul was able to shoot normally, confident that the editorial team could unwrap the images and create an HDR image from them.

“The workflow turned a Digital Imaging Technician (who oversees on-set data capture) into an on set colourist helping the DP to adjust the image,” he explains.

Having validated the look on Dolby Vision monitors before shooting, the on-set colour metadata was ingested and tracked through Avid, and graded and conformed on Da Vinci Resolve, retooled to function in HDR by Blackmagic Design. A BVM-X300 monitor was used for viewing although Valentic would like monitors that can sustain even greater than 1000 nits of brightness.

“We’re not just conforming picture and sound but also conforming colour,” says Valentic. This allowed Deluxe New York colourist Martin Zeichner to finish the grade in HDR and SDR in parallel by monitoring both outputs.

“An HDR image looks fantastic but there’s no point doing it if not everybody can enjoy it,” says Valentic “The volume of consumer HDR screens is very small at present and I have to guarantee to the client that the image will look as good in SDR as in HDR.”

The project was passed through a Dolby Vision monitoring and encode process to ensure that the HDR files were interpreted correctly on Dolby Vision-enabled screens.

He admits to making many mistakes with HDR in the beginning. “I behaved like a child with a new toy,” he says. “I’m fortunate to have worked on a project of this size in order to learn the pitfalls – what works and what doesn’t.”

He elaborates, “You have these incredible greens and purple tones but you don’t necessarily have to use them all the time. Whereas in SDR the highlights are just white, there is literally no colour and the blacks are not true blacks, with HDR suddenly we have full control over the spectrum. There’s an incredible depth to shadows because of the new levels of contrast.”

Creating separate masters only contributed an extra half a day in the grading suite, because of the time spent in preparation. “We don’t come to the grading suite trying to invent the look,” explains Valentic.

Valentic is preparing an HDR commercial to be shot Red in South Africa where the DP will have the luxury of see images in either HDR or SDR on set in realtime.

Tomorrowland, Stephen Nakamura, Deluxe’s Company 3

A number of theatrical feature films are being mastered for distribution on Blu-ray and streaming to services like Netflix by studios including Fox, Warners and Universal.

Stephen Nakamura, senior colourist at Deluxe’s Company 3 in LA has done a number of home distribution HDR remasters. He says he begins his translation of the HDR grade from the original version which has worked on the most whether that’s the Rec.709 grade or the P3 one (P3 is the colour specification for theatrical or Digital Cinema Initiatives/DCI masters).

Nakamura has created a conversion LUT (look up table) to help him in the translation. “It gets me in the zone but each movie needs to be massaged depending on the content. It’s not a one size fits all process.”

In Walt Disney’s 2015 feature Tomorrowland, director Brad Bird used HDR to create a distinction between storylines in the ‘real world’ which were of darker tone than those in the brighter futuristic Tomorrowland.

The blackness of night scenes is so much deeper but you can see more because with HDR more light is being pushed into the picture,” says Nakamura who HDR graded the title for Blu-ray release.

“It is in scenes like that where it really sticks out. With a regular real life drama you may not want the story to appear really bright or really colour saturated because you want something that feels right for the story.”

The Man in the High Castle, Thor Roos, Deluxe Encore

Amazon Studios’ alternate history of a Nazi-run United States was shot largely in Canada at 5K on Red Dragons.

“From the get-go having the show look very theatrical was important to Amazon,” explains Thor Roos, senior colourist at Deluxe’s Encore Vancouver. “They wanted to give this 1960s universe a realistic feel.”

Roos says good original photography will deliver the best results in HDR but that the effect will reveal subtitles in everything from set design to costume. “You can see more detail in 4K but HDR takes this to a whole other level. You can see detail in neon lights in the background, spectacular highlights in windows or stained glass. HDR really shines in those moments.”

With Encore supervising editor James Cowan, Roos opted to grade the UHD HDR alongside a HDR Rec.709 version.

“We had a lot of creative discussion about how to approach it,” says Cowan. “Should we grade HDR first and make the Rec.709 version match that or vice versa? We decided that Rec.709 was the hero path because ninety-nine percent of people will be looking at that. That said, we colour corrected both deliverables side by side. We’d take scenes and shots, evaluate them both, see which grade looked best and select that.”

Amazon dictated that the production use OpenEXR, an open source HDR file format originally developed by ILM. Roos monitored the HDR path on Sony’s BVM-X300 and checked regular plasmas for Rec.709 with Resolve used for conform, colour, titles and versioning.

Cowan estimates that the process added a third more time in the grading suite with knock-on costs to storage and GPUs to power realtime compute performance.

A scene in the first episode depicts several characters on a bridge at dawn watching the sun rise. “HDR made the sunrise look beautiful while allowing us to see the actor’s faces rather than being silhouetted, which is the effect you would get with SDR,” describes Roos.

Pablo Garcia, 4K Workflow Specialist, Sony

“The ideal source material for HDR would be 16bit RAW footage, shot using a camera with a very wide gamut, preferably one that’s Rec.2020 compliant. High bit depth is essential for dealing with Rec.2020 and HDR.

Workflow

While workflow on set doesn’t change, the display technology does which means ensuring that scopes and monitors, software colour science, and calibration tools can all handle HDR.

The systems I’m using right now to post HDR are both DaVinci Resolve 12 and Filmlight’s Baselight, coupled with Sony’s BVM-X300 reference monitor and the Leader LV5490 4K multi waveform monitor. Colour science is key, and both of these systems have developed very consistently. Not all the available systems have this advanced colour science, nor the monitoring tools to verify.

Deliverables

When it comes to deliverables, separate grades are still, due to the differences in colour spaces and gammas (709-P3). The implementation and development of the two standards - ST2084 and HLG HDR - will tell us if more passes will be needed. Also, ST2084 is a device dependant OETF and might need different grades for different nit level, though we’ll have to wait for the standardisation of HLG to know for sure.

What I’ve found easier is that separate mastering passes for HDR don’t need to be performed on a shot-by-shot basis, but on a scene-by-scene basis, in order to control peak levels and saturation of the RGB channels.

Creative options

Here’s where things become more interesting. HDR gets rid of many of the limitations we’ve had so far – such as narrow colour gamut and gamma – so choosing how to use it becomes a purely creative choice. As a friend of mine told me once “just because my car can do 200mph, that doesn’t mean that I need to drive it at 200mph all the time!’’. Setting light, exposure, and production design are all fields open to exploration.

Light and colour have always been a major part of the story telling process and now, depending how you use it, can add even more dramatic results to the mix.

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