Thursday, 25 February 2016

High Dynamic Range: Stepping Out of the Shadows


Broadcast Tech p46 

HDR promises to take footage to a whole other level, capturing TV images that offer unprecedented detail and texture even in the shadows.


The Man in the High Castle
Amazon Studios' alternate history of a Nazi-run United States was shot and post produced 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-owned 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.”

HDR can be applied after a project's grade or, in some cases, before colour correction but, 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.

Lacking on-set monitoring, series DPs Gonzalo Amat and James Hawkinson could only view HDR in post but as they saw more graded rushes they began making adjustments on set for exposure and lighting.

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.



Marco Polo
Hired to work as colour scientist for season 2 of ten part Netflix drama Marco Polo, Dado Valentic, founder and chief colourist, 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 Valentic won't reveal but it 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 colorist Martin Zeichner to finish the grade in HDR and SDR in parallel by monitoring both outputs.

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. There will be a period when everyone is excited by what is technically possible with the image rather than with what the emotional and creative content of the storytelling requires.”

A scene in Marco Polo features an actress against the backdrop of a rain storm walking from outside into a dark room. “You would not normally be able to cover this and see all the detail in the shadows or on her face but in HDR this is a revelation,” relates Valentic. “DPs will no longer have to compromise by having to select which part of the image they want us to see.”



Good Girls Revolt
Amazon episodic newsroom drama Good Girls Revolt was shot on Red Dragon with the post route from dailies to editing kept in rec.709.

The recommended practice is to start with the HDR version and extract from it a regular HD rec.709 pass but the practical reality of TV is that the majority of storytelling and viewership is in rec.709,” says Pankaj Bajpai, senior colourist, Encore Hollywood. “So we devised the aesthetics of the show in rec.709 and then did the HDR.”

Since HDR opens up a new creative palette to producers, DPs and directors, Bajpai feels it's the job of the colourist to marry their needs with the current restrictions on viewing technology. “Achieving that balance is a huge aspect of how we manage the HDR and SDR versions,” he says.

HDR is at its most dramatic in content with high contrast between light and dark scenes, in explosions or on metallic objects offering opportunities for light reflections. Science-fiction or big budget action movies are obvious beneficiaries. Less so are low key dialogue-heavy sequences.

I found that if you have a scene in a living room with two people talking on a couch illuminated by a lamp then, in the HDR version, the lamp will appear very bright and actually start to compete for the viewer's attention with the actor's performance,” says Bajpai. “We tried to keep the basic aesthetic of the show as approved in rec.709. There isn't one scene that stands out dramatically differently in the HDR pass but what you experience in HDR is greater texture and depth in the shadows and midtones.”

Examples in 1969-set Good Girls Revolt are the definition of the sky reflected in the glass windows of New York skyscrapers and hotel lobby chandeliers and marble which appear “as if you can touch them.”




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