True colours: delivering in HDR

High Dynamic Range offers incredible creative possibilities for filmmakers but, at this stage, few have delivered an HDR project. Jon Creamer talks to some of those that have about their experiences with the medium so far

High Dynamic Range content allows filmmakers to show the world on the screen almost as the human eye sees it in real life, with vibrant colours, dazzling light and incredible detail. Right now though, HDR content that the viewing public can tap into is fairly limited. Amazon and Netflix are broadcasting a selection of shows in full HDR glory, Blu-ray is another outlet and the BBC, Sky and BT are all experimenting with HDR. HDR content will ramp up, but at the moment very few producers and post producers have been asked to deliver in HDR. Those that have often become cheerleaders for the medium, describing it as a step change from SDR. We’ve asked a selection of production pros how they’ve approached HDR so far.

Planet Earth 2
Films@59

Bristol’s Films@59 delivered the SDR version of the BBC’s epic Planet Earth II series and was also asked to deliver an HDR version of the programme. Post producer Miles Hall and inhouse colourist Christian Short explain how they did it

What were you asked for?
MH The decision to deliver in HDR was taken relatively late in the day which meant we had to think carefully about the workflow as the series was predominantly an SDR delivery. We had to adopt the HLG standard which is the BBC and NHK devised Hybrid Log Gamma rather than using a Dolby PQ or Dolby Vision method.

What did the grade have to achieve?
CS The SDR version was graded by Adam Inglis and the key thing was to make sure the original grade translated through into the HDR grade while using as much of the ‘HDR-ness’ of some of the imagery to make those shots pop. Some scenes are shot in flat light and some are in dappled light under forest canopies and so on. We could achieve an overall lifting on the flatter light stuff but the stuff that was shot in HDR-centric environments really did pop and we could play with masking areas to bring certain highlights out. It’s the first HDR experience we’ve had. We’ve done a lot of tests and seen a lot of examples but we were feeling our way on the first programmes. Certain scenes you can do a lot with, others you just lift them and bring them into HDR space

What was different about working in HDR?
CS From my perspective, the environment I’m working in now has to have much brighter ambient lighting than it would do if I was grading in SDR. Frequent eye breaks are needed too because it is super bright and it does fatigue you. You feel smashed at the end of the day compared to grading in SDR though I imagine if I was grading in HDR all the time I’d get used to the muscle strain. Also, when you’re grading an HDR version and then grading something in SDR, as a colourist you need a good clear day to reset your eyes. It’s a good idea not to bolt those sessions back to back.
MH What’s tricky is when you go from the HDR to the SDR version, it’s a bit of a let down. That’s something for producers and post producers to get their heads around because when something looks amazing in HDR, when you come back to it in SDR you might think it’s a bit disappointing.

What needs to be thought about beforehand?
MH You need to plan your workflow carefully and talk to your post house about what the deliverable is because there is more than one flavor of HDR. There might be more than one HDR deliverable so while you might deliver HLG through the BBC, when you go to Blu-ray they might require PQ, so there are additional processes you might have to go through to transform your HDR between standards. You will have to repeat processes. We’re working very hard to try to establish a workflow that will minimise the repeating of vfx work and so on. Noise reduction is very important when delivering in UHD, not just HDR. What you can get away with in SDR HD is a lot more than you can in UHD HDR. There’s definitely an uplift on top of the SDR version, at the bare minimum you have to grade for the HDR. It’s not something you can do as an after thought.

Ex Machina
Molinare

Molinare colourist Asa Shoul created the original grade for Ex Machina and returned this year to grade the film in HDR

What was the brief?
To recreate the film in 4K and to reflect the original graded look and feel as closely as possible. Creatively we needed to represent the original film but, in 4K, there were several scenes that lost the key characteristics of look and feel when using the original grade settings. We revisited these, taking advantage of the wider range of colour space and contrast to deliver the original look and feel but taking it to a new level. We were conscious of the danger that all our options might accidentally lead to a completely new look, however to avoid this we constantly referred to the original material. On a standard Rec709 monitor we had the original grade so that we could use this as reference when doing the HDR.

What was the creative upside of HDR?
HDR offers greater freedom and choice in the creative process. The opportunity to highlight key sections of the image, bring greater depth of field, underpin the emotion and excitement of sequences is even greater. We can achieve even more during post production than before. However, used unwisely, HDR can be unforgiving. Its power needs to be harnessed. There is a danger of overwhelming the viewer, thus losing the creative intent but, with sensitive use and a creatively controlled approach, it offers fantastic new creative choices.

Did any scenes really lend themselves to HDR?
In the scenes where there was a power cut and the red safety lights came on, when grading in P3 and Rec709, we found that the saturation of the red was never quite as rich as we would like, whereas in HDR it was stunningly rich and vibrant. Also because of the extended greens in Rec2020 (HDR) exterior forest scenes took on a more realistic quality, transporting you to that environment.

What advice would you give to others working in HDR?
HDR offers real creative opportunities but it can be too powerful. The enhanced colour and contrast offer so much more for storytelling. However it needs to be used with care. DoPs and colourists need to fully understand what it offers and apply their experience to harness the capabilities in a measured and creative way. With both a creative instinct and a technical understanding these tools offer fantastic freedom in post for filmmakers.

Inferno
Company 3

Company 3 colourist Greg Fisher on the HDR delivery for DaVinci Code sequel, Inferno

What was your approach to delivering in HDR?
I was actually a little wary of HDR before actually trying to grade it. The first demos I had seen were basically just the same images, but brighter, so I wasn’t too impressed. Today I think it is understood that you are trying to deliver more dynamic range but maintain an image suitable for its display scenario, which is what I found worked well whilst grading Inferno. In terms of my workflow, I would first use DaVinci Resolve to make sure that the HDR frames appeared similar to the SDR version. I then used Resolve’s grading tools, including log grade, highlight and soft clip controls, to carefully control the roll off. Ultimately, this made the images much more lifelike, with a significant improvement in sharpness despite no change in pixel resolution or file size.

Are there any scenes that really lent themselves to HDR?
The first time we meet the lead, he is in hospital, disorientated, confused and suffering from amnesia. This is emphasised by lights flickering on and off while he’s in his bed. When watching on the 4000 Nit Pulsar monitor, you actually feel the heat of the flashes in your eye and your iris playing catchup. This puts the audience with him in his state of mind to a far greater extent than is normally possible.

What advice would you give other colourists?
Embrace it. Real black in a cinema is a revelation, as is the extra sharpness. It feels like a significant progression.

Various film projects
Technicolor

Technicolor’s senior supervising colourist, Peter Doyle has delivered features in HDR including Miss Peregrine’s Home for Peculiar Children

What do you need to look out for when working in HDR?
Poor image processing techniques and “dirty” LUTs and transforms are exposed to a much greater degree in HDR. Noise and grain take on a less attractive sensibility, it’s not so easy to hide a less than perfect key or colour separation behind grain. LUT and transforms need to be as wide and deep as possible.

What do you have to think about when delivering in HDR?
Does one reproduce the Rec709 grade on a HDR monitor, or do you take advantage of the extended dynamic range and colour gamut? Does the original photography have the dynamic range to justify opening up the contrast ratio? When grading on a 14 F/L xenon what was felt to be a compromise from a dynamic range stance and should HDR be used to put it back?
What are the difficulties you encounter? Locking down display device specifications and coordination between the various studios differing specs and requirements creatively…it’s always about maintaining the patina and look of the 14 F/L xenon grade. This takes more than a LUT and trimming the colour. It’s about reproducing the flare, cross-colour distortions and the very experience of seeing an image reflected on a white screen to an image reproduced by an light emitting device.

What’s the creative upside of HDR?
Greater dynamic range and colour gamut and finally getting away from Rec709. 709 has served us well, but it had its issues, that have become an accepted look. To be able to take your DCI XYZ grade and reproduce in rec 2020 for a video deliverable is almost an epiphany.
HDR is not just a technology, it’s a toolset for the creatives.Skin tones stay intact, specular’s and highlight modeling are reproduced without compromise. Indeed there is a subtlety returned to the reproduction of the lighting that’s fantastic. It gives great access to performance. Delicate reflections and colour hues can be displayed without needing the sledge hammer that’s needed for Rec 709.

Fleabag
The Look

The Look colourist Thomas Urbye graded BBC3 and Amazon sitcom Fleabag which also had to be delivered in HDR

As the vast majority of the audience will be seeing Fleabag in SDR it was important to me and DP Tony Miller that we got sign off in Rec709 on each episode. We then moved on to the HDR version where I was trusted to keep the integrity of the image intact. The whole series was shot on the Arri Alexa in ProRes 444 at 2880×2160 with anamorphic lenses and the entire workflow was maintained at this resolution.
Once the SDR version was signed off our attention moved to the HDR versions. Amazon had specced Rec2020/2084 (PQ) and we were told to use the Sony BVM X300 monitor in UHD. Thankfully the Quantel Rio uses transfer curves at 16bit float to move you from the Rec709 colour space in to Rec2020 & PQ and the image and grade is essentially maintained. However, at this stage, any clamping on highlights and colour saturation is released and the image visually comes alive in highlight areas. Detail that was formerly lacking outside windows and in bulbs suddenly takes on real shape and even skin tones seem to have a new sense of life about them. I had a Sony OLED in Rec709 showing me the episode in SDR and then simultaneously on the Sony BVM X300, the HDR grade. It was important to me that I maintained the same feel in HDR and to not fall in to the trap of pushing contrast or over-saturating the image. Contrast ratios do increase by the nature of the highlights being unclamped in PQ, so care has to be taken that mid tones in the image are lifted slightly to create the same visual intention.