Let's get high: the route to HDR

From the shoot to post to final delivery, Michael Burns discovers the best route to HDR

The long-awaited promise of high dynamic range (HDR) TV series and programmes is now being delivered, appearing on (compatible) screens with greater regularity. But if you’re thinking of going down this route, how should mastering to HDR change the way you approach projects from planning and production management, and from shooting on set to the post workflow and grading? And why go to all  this trouble?

Post planning for HDR
Streaming services, particularly Netflix and Amazon, are throwing a lot of weight behind HDR, and facilities are picking up more and more work on the format. “We’ve been mastering shows in HDR for Netflix, Amazon, Fox, Hulu, Sony, among others,” says Encore md Morgan Strauss.

The Farm has mastered several high-profile projects in HDR for Amazon and Sky. Peter Collins, head of scripted pipeline at The Farm Group, says the main impacts in terms of budgeting are those of storage and delivery, throughout every stage of the project lifecycle.

Production requirements include shooting at higher resolution, meaning larger data sets from the cameras, while post requires larger storage allocations to store Digital Intermediate files at both a higher resolution and higher bit depth, says Collins. “Then there’s the additional network overhead that comes along with that, while the archival delivery masters to the commissioners requires more storage allocations again.”

investment needed
Goldcrest CTO Laurent Treherne says being able to deliver 4K HDR content requires substantial investment. “First you need to be able to display HDR content, and a grade 1 HDR monitor is quite expensive,” he says. Goldcrest uses the Sony X300 monitor for all video SDR and HDR deliverables. “You also need to be able to playback and grade uncompressed UHD resolution 16bit files,” he adds. To give an example, an uncompressed 16bit UHD/HDR file is nearly six times heavier than a standard uncompressed 10bit HD file.

Accommodating HDR has been the biggest investment the company has made, says The Look CEO and senior colourist Thomas Urbye. “We combined the need for 4K workflows, monitoring and delivery with HDR support. We have installed a 100Gb network to move 4K 16bit data like HD 10bit data, and the machines are using very fast graphics cards – we can’t afford for these big dramas to be waiting for copying or rendering.”

HDR flavours
One key factor in planning seems to be the flavour of HDR being used. Encore’s Strauss says: “Both of the prominent flavours, HDR10 and Dolby Vision, are very similar in terms of the colour science.” But their workflows can vary. Dolby Vision is a simplified, prescribed workflow using [Dolby] proprietary software and hardware. HDR10 is delivered through off-the-shelf platforms like Resolve, Baselight, and Lustre. “There are a few extra hoops to jump through depending on whether it’s Dolby Vision or HDR10.”

Poduction budgets are starting to reflect these kind of investment, says Peter Collins who adds: “The feedback from our clients is that the creative opportunities that the technologies have to offer have been well worth the budgetary increases.”

Shooting and lighting in HDR

Though attention is focussed on HDR as a post process for now, other stages of the production need to take heed of the difference in approach.

Fleabag, the 2016 foray by the BBC into HDR, saw Liz Pearson take on the role of post-production supervisor (working with The Look). “A lot of people think [HDR] is just a new flavour of HD. And it’s not,” she says. “It’s more like you are shooting film, than data.” Departments like camera and make up need to be briefed beforehand, “It’ll show everything up – every makeup line, every hair, every shadow.”

Monitoring on set
Although it’s an expensive extra, Pearson recommends an HDR monitor on set, and having someone assigned to checking for the differences – the hard-pressed DIT can expect to be even more busy as HDR begins to roll out.
“HDR reveals things that you may not have been aware of in an SDR version,” agrees Molinare’s Chris Rogers. “If HDR isn’t considered on set, then lights and other bits of kit that were lost in ‘blown out’ windows may become obvious in HDR.”

Films at 59 project manager Miles Hall says noise reduction is a key issue as HDR exposes a lot more. “The greater dynamic range also requires more accurate graphics and VFX; they have to be spot on.” Camera choice is important too, particularly in genres like natural history where a wide range of cameras are used. “HDR is pretty unforgiving of certain camera formats,” says Hall.

Maximum latitude
The Farm Group’s head of scripted pipeline, Peter Collins, says files should either be recorded as a raw format, or as a de-Bayered log image using the widest colour gamut possible. This ensures the maximum colour latitude is available in post and for archive.

“There are certain conditions where a combination of shutter speed and motion within the frame can introduce visible judder in high dynamic range images at current common frame rates [24/25/30 and so on],” Collins adds. “So it’s advisable to consider this when shooting motion in scenes with a lot of light, or when panning shots.”

Technicolor head of broadcast Louise Stevenson says her facility will do tests with the camera department to check how HDR process will impact lighting and composition. “For example, practical lights in the frame can become very bright and distracting.”

She also warns that HDR should be used effectively. “Highly saturated colours may not benefit a period drama, for example,” she adds.

“It is even more important to capture well-exposed images, as a 4000 nits HDR grade can be unforgiving with noise or clipped highlights,” continues Stevenson. “Shooting with high dynamic range cameras such as those from RED, Alexa, Sony or Panasonic will give the best possible results.”

Encore MD Morgan Strauss says production values will shine through with HDR. “Something you may not have noticed in the background due to contrast or gamut limitations may become clearly visible in the larger colour gamut HDR pass. It could be that a translight behind a window is more obviously not an actual cityscape.”

Sensitive shooting
Encore senior colourist Tony D’Amore also stresses how much HDR is sensitive to highlight ratios: “In production, if you establish a strong ratio, you have to make sure to balance that with translights or backdrops, and outside lighting. The outside level has to match, or it will be obvious. Also, be careful not to clip highlights in camera, especially if you plan to shift the colour drastically in post.”

“Ideally all images would be viewed on an HDR monitor on set,” stresses Peter Collins. “However, any unforeseen issues caused by the higher contrast can be somewhat mitigated or completely eliminated in post, while retaining the original creative intent of the scene as shot.”

The post workflow
At Films at 59, most of the HDR experience to date has been with the natural history film making community in Bristol. Due to the very long lead time on these productions, the HDR requirements have been an added extra rather than being part of the original deliverables.

Project manager Miles Hall says: “As natural history productions tend to be shot in the log formats that we need for HDR anyway we didn’t need to change to our approach too radically.”

HDR or SDR first?
The main issue is whether to take a programme through post in HDR and make the SDR pass at the end, or whether to post in SDR first and to treat the HDR version as separate. After all, the SDR version is the primary deliverable and one that 99% of people will see.

“Either way raises its own issues and we work with production teams to determine the best approach for them,” says Hall.

Films at 59 has delivered Planet Earth 2 and Blue Planet 2 using the HLG standard. This was a relatively straightforward process, says Hall. Film at 59 could adapt its hardware to meet the standard and still maintain its typical workflows so everyone including clients were comfortable with the process. However, the Dolby Vision standard, and the archival requirements of broadcasters like Netflix, have meant a significant change in workflows. “We have had to adopt a more film/DI based workflow that allows us to finish in the kit that supports the Dolby standard. This means having a workflow that manages the colour pipeline between graphics, VFX, online and grading platforms to make sure we maintain the integrity of material through the process.”

The Farm’s Peter Collins agrees that post production workflows have had to adapt to a DI pipeline with HDR. “This involves efficient and flexible colour management to facilitate the additional requirements for grading and final mastering,” he says. “In addition, the size of the data sets necessary for HDR work require more resources from an infrastructure perspective including storage, networking and monitoring.

“Any kind of technical compromise on the picture quality is visible in HDR,” continues Collins. “The grain or noise needs to be managed more closely. A limited bit depth or any sort of compression on the media could be ok in SDR but could become a problem in HDR. So it’s very important to optimise the image pipeline quality throughout the full post workflow in order to guarantee the best quality for the HDR masters.”

HDR10 vs Dolby Vision
Goldcrest typically works with HDR10 and Dolby Vision for both domestic and theatrical deliverables. “The process is slightly different between HDR10 and Dolby Vison domestic deliveries,” says CTO Laurence Treherne. “With HDR10 you are only delivering a 1000 nits HDR version of the content. The SDR version is a separate process with its own grade. For Dolby Vision, you are delivering a single ‘package’ which could include multiple delivery formats – 4000nits HDR, 1000nits HDR, SDR, and so on. All those versions are usually done from the 4000nits HDR grade. You then use the Dolby Vision process to derive and trim the other versions.

“We do not own a Pulsar monitor or a Dolby Vision HDR projector so the main challenge for us was to find a way to do those HDR passes without having to move the media and projects to Dolby in Soho Square,” continues Treherne. “We discussed a few options with Dolby and agreed to look at a remote solution based on a dark fibre link between our two buildings. This setup allows us to remotely control any of our editing and grading platforms from the Dolby building and send the HDR uncompressed 12bit video signal back from Goldcrest to Dolby in real time. Our colourist is sitting at Dolby, but all the hardware, media and project is still located at Goldcrest.”

Trim passes
“The setup is slightly different depending on whether we’re delivering for the Dolby Vision system or HDR10,” says Technicolor’s Louise Stevenson. “When working on a Dolby project we do the HDR 4000 nits grade first and then create the SDR 100 nits trim – and possibly 1000 or 600nit after that. The trim passes require the use of Dolby’s own CMU analysis system. For HDR 10, we typically do the SDR version first and then do a separate 1000 nits pass. If we are doing the HDR version first, then this becomes the primary grade, so we will discuss the setup for this during pre-production.”

Prepping for the future
“As we are doing a lot of Netflix shows and have to use Dolby Vision it’s a prerequisite that we have to do the HDR first, especially as we aren’t even delivering an SDR deliverable,” says The Look CEO and senior colourist Thomas Urbye. “Having now done this on Netflix’s The Innocents series using Dolby Vision, I would actually always start with the HDR and use the Dolby technology as a fast track to the colour space conversion, even if we still dug in and did some more shapes and tweaks along with it for an SDR file export.”

“So far we have always been asked to start from SDR and then create the HDR master as an additional delivery,” says Treherne. “Saying that, doing the full post from online editing to grading and mastering in HDR wouldn’t be a problem for us. I wouldn’t be surprised to see the process flipping the other way around relatively soon. Most [new] TVs are now HDR compatible, but I think the real trigger for doing the full post in HDR will come from having the onset grade and offline editorial done in HDR. It will then make sense to post in HDR and make the SDR delivery as an additional pass at the end.”

Grading HDR
The BBC’s Planet Earth 2 and Blue Planet 2 were both delivered in HDR formats by Films at 59, so project manager Miles Hall knows well how imagery can benefit from HDR. “You can exploit specular highlights and environments with wide variations in light,” he says. “For example, light coming through a jungle canopy, or the sun reflecting on water or ice flows. HDR in these instances give you a much closer representation of real life than we are used to.”

The Look CEO and senior colourist Thomas Urbye sees the creative benefits in scenes with dynamic range and colourful landscapes, costumes or interiors. “The images can be absolutely stunning – far more impressive to the eye than REC709 SDR,” he says. “We have been showing our clients who have HDR dramas coming up some HDR material, so they understand what will happen in post. They have been blown away by it – the word ‘breath-taking’ is used a lot.”

Time to be creative
Narduzzo Too colourist Vince Narduzzo’s most recent HDR project was Save Me (World Productions) for Sky Atlantic. “It allows you to be more creative,” says Narduzzo. “Less time is taken trying to find detail in the image and more time can be used just enjoying the amazing range you have at your fingertips.”

“The big difference is the latitude and available information within the image,” he adds. “This is fantastic but at the same time care needs to be taken to ensure you retain an image that works.”

Narduzzo also warns about overdoing the grade. “You still want a piece that flows and doesn’t shout out,” he says. “Also, extra detail is great but sometimes not what you want. These are things that can be addressed. I think most programme makers still crave for the look of a 35mm frame and this can be achieved. Don’t end up with something eye popping but crude.”

Senior colourist at Molinare Chris Rogers is currently working on The Widow, a new HDR drama for ITV and Amazon: “The images are simply more striking and are a closer representation of how we perceive the world,” he says. “The additional dynamic range and gamut give us the opportunity to push images in new ways. This doesn’t mean that we will want to grade every scene to the limit, but it’s certainly nice to have the additional scope.

“There are some important considerations when approaching an HDR project,” he adds. “Some of the techniques that colourists have traditionally used to shape the look may only work well in SDR. For example, conventional ‘print emulation’ LUTs are problematic at best, so we now need to consider how to approach a grade that will translate easily and maintain the intent between various display colour spaces.”

Bolder colours
“Certain colours are bolder in the wider colour gamut,” says Encore senior colourist Tony D’Amore. “From a storytelling standpoint, there’s a much wider colour spectrum to work with. Cyan, blue and red will be bolder. If you’re going for a stylised look, those colours tend to be really striking and can evoke emotion. But that vibrancy doesn’t necessarily translate to SDR, which can be a challenge. It’s a reason to preview both versions as you go.”

Most recently D’Amore has graded Marvel’s Jessica Jones season two, Luke Cage season two, Iron Fist season two and Daredevil season three for Netflix in Dolby Vision. Additionally, he is currently mastering Legion season two for FX in HDR10.

Planning the grade
“When grading in HDR, I lay out a plan, starting with a custom wide colour gamut LUT for the specific camera/project,” continues D’Amore. “Next, I set a few looks in HDR then immediately preview them in SDR to ensure that I haven’t lost any potential highlight detail and to see if the look holds up. This approach is especially important with HDR10; with Dolby Vision, I do the HDR and SDR grades simultaneously. This is nice because it saves me a step and is easier on the eyes. Also, Dolby Vision currently allows highlight detail up to 4000 nits – four times that of HDR10. This is a variable that is crucial when balancing between shots. You will be surprised how much colour hides up in the highlights in Dolby Vision HDR.”

D’Amore says the Dolby Vision Content Mapping Unit (CMU), which applies the grading decisions as dynamic metadata, does a good job at previewing the SDR grade. “But it does require some HDR finessing to make sure both versions look perfect,” he says. “This is an important step to ensure that the look holds up in both HDR and SDR before committing to it. The goal is get as much latitude out of camera material as possible.”

Technicolor’s Louise Stevenson also stresses the importance of taking time with this SDR ‘trim’ during Dolby Vision grading. “This version will be seen by a large percentage of the audience, so it is essential to take care with this pass to make sure all of the creative team are satisfied with the results,” she says. “It can take time to ‘tune-in’ to the lower contrast look of the SDR version when everyone has been used to the HDR grade, especially if the HDR version has been pushed creatively, so it is important to manage clients’ expectations of what can be achieved in SDR. For HDR10, we typically do the SDR version first and then do a separate 1000 nit pass.”

“It is essential that the post house is geared for this new format [HDR], it needs great care and attention to ensure a smooth post experience,” says Vince Narduzzo. “I am pleased to be in on the ground floor as it’s an amazing advance, I would say bigger than the transition from SD to HD; this is actually giving better pixels not just more.”