Colorists: Your Job #1

“If you come to me tomorrow and you say ‘Hey, I’ve got an HDR project I’d love to grade with you,’ I’ll say ‘Okay cool’, and very early on in the process I’m going to say ‘Let’s set our speed limit in terms of luminance.’ And if you ask me for my take and you want to go with my suggestion, I’m going to suggest that we set a speed limit of around 250 nits because I don’t want to see an image brighter than that.” – Cullen Kelly, colorist

Setting The Speed Limit Is Job #1 

When asked if he had any tips for those undertaking Dolby Vision HDR grading for the very first time, Siggy Ferstl, senior colorist at Company 3, gave the following advice:

“Understand the look [that] the filmmakers are wanting and establish early on the sort of bright[ness] levels, how far you want to push the highlights… That’s probably […] the number one thing to establish before you even start doing the creative color… That will change the look of the show and also, if you say for instance go too bright in establishing that light and then you get into coloring, it can put a lot of extra work on you if you’re having to sort of force the highlights down the whole time.”

What It Means To Set A Speed Limit

Setting a speed limit means defining your target peak brightness (in nits) and highlight roll-off philosophy early on. Before diving into creative color, the most critical decision an HDR colorist makes (in collaboration with the DP/director) is establishing the project’s target peak brightness (nit level) and highlight philosophy. It is arguably the single most important foundational decision for HDR grading.

Cullen Kelly: Do you impose a hard speed limit on your projects?

Corinne Bogdanowicz: I don’t have a hard rule or setting that I use. [It] depends on the project. I rarely peak things at 1,000 nits. Most people don’t react well to things being that bright. I generally start with a roll off but I could still go up to 600 nits. If it’s a much softer show, we’ll maybe do 300 nits – maybe even less. But again, it might change scene to scene. There might be some brighter scenes, there might be some scenes that are softer, so it just kind of depends on what we’re doing.” 

Why Setting A Speed Limit Early On Is Crucial

HDR’s expanded dynamic range isn’t about making everything dazzlingly bright. Establishing peak highlight levels early on ensures that brightness serves the story, not the technology. Defining how far you want to push the highlights encourages a conversation about the look and mood before the technical work begins.

Prevents Headaches Later On

As Ferstl explicitly states, setting this limit early prevents a massive workflow headache. If you start grading without a clear peak target, highlights naturally tend to creep higher during creative exploration. Realizing later that these highlights are too aggressive means you must painstakingly lower them across potentially hundreds of shots, which is far more time-consuming than establishing a limit upfront. 

Provides For A Unified Grade Across The Project

HDR projects not infrequently involve thousands of shots graded by potentially multiple artists over weeks or months. A clearly defined peak brightness target is the anchor point for consistency.

Defining A Peak Informs Roll-Off

Defining the peak isn’t just about a hard ceiling; it informs the roll-off – how highlights transition to that peak. Establishing this early ensures you preserve texture and detail in bright areas gracefully, rather than accidentally clipping or creating harsh transitions that need fixing later.

In sum, setting a speed limit should be the cornerstone of any HDR workflow discussion.

“Some of the worst practices I’ve seen in this industry have been people dumbing down the HDR [grade] because a DP comes in the room and says they don’t like highlights, so they put their highlights at 200 nits. And then now they’ve basically graded SDR on an HDR display. And I don’t care if you’re doing HDR10 dual pass, if you start with a master that’s got such low contrast, the CMU is going to see that and be like ‘What do you want to do here?’ and it’s going to give you a pretty flat, muddy picture.” – Tony D’Amore, Senior Colorist and Director of Creative Workflow, Picture Shop

Studios Do Not Dictate Peak Brightness

In 2019, the major Hollywood studios issued a joint statement asserting that the brightness or darkness of each shot of a film is up to the filmmaker:

“It is also worth highlighting that a critical feature of the HDR system developed by DCI is one of creative expression. An HDR DCP need not exercise the entire range of brightness offered by the HDR specification. Despite the peak luminance that an HDR system is capable of, the brightness or darkness of each shot of a movie is always up to the filmmaker. It is not up to the HDR projector or display, which simply provides the full range of capabilities. DCI seeks to ensure that the headroom required to reproduce a filmmaker’s creative vision exists, whether that be the darkness of a cave, a candle, a car’s headlights, a meteor, or sunlight spilling through a window.” – DCI 

DCI is a consortium of major motion picture studios formed in 2002 by Metro-Goldwyn-Mayer, Paramount Pictures, Sony Pictures Entertainment, 20th Century Fox, Universal Studios, The Walt Disney Company and Warner Bros.

A number of colorists have confirmed that studios rarely raise objections pertaining to peak brightness.

“You can make images on an HDR screen identical to the range you had in SDR, if you want. No one should, or will, as far as I’ve heard, force you to make the image higher in contrast than you are comfortable with. If your vision is to limit and roll off all highlights (to where they would be in the old SDR TV or even film print) you can. It’s your creative choice. A streamer may query it, but it’s unlikely they will force you to grade to a maximum brightness (or nit value as it’s known). – Thomas Urbye, colorist (Sex Education, 2019-2023)

Key Distinctions Between SDR & HDR Highlights

In traditional photography, the term ‘highlights’ is sometimes used to refer to any detail near white, such as bridal lace, which may entirely consist of diffuse reflective surfaces, [while] in HDR literature, the use of ‘highlights’ is intended for the specular or emissive regions in an image since that is a key feature opened up by HDR. – ITU-R BT.2390

“The cinematographer’s job to do good HDR is don’t clip the signal.” – Juan Cabrera, Senior Colorist & Founder, LightBenders

SDR signals provide little “headroom” for highlights. Whereas clipping of highlights is quite common in SDR content, it is uncommon in well-graded HDR content, which is one of the fundamental differences between SDR and HDR imagery.

Rolling Off Highlights Prematurely

“And now, if we think further about negative emulation, all kinds of other interesting questions come into play that kind of go along the lines of what we were just talking about, like what are the great things and also the limitations of a film negative. Here’s one that is not popular and people don’t like to talk about: film negative doesn’t have the dynamic range that a modern digital sensor does. It just doesn’t. So, what do we do with that? Do I want to mimic the lower dynamic range of a film negative? That’s not the craziest thing in the world but it’s also another example of the type of subjective question we have to answer if we’re going to emulate film negatives – like, what parts do we want to emulate? Do we really want to emulate that part? I don’t necessarily see a benefit to rolling off my highlights prematurely that otherwise would be preserved and available to me in a grade. I’m not sure what the benefit is there.” – Cullen Kelly

Highlight Roll-Off Is Non-Negotiable

Highlight roll-off is a characteristic of photochemical film that many believe is as important as dynamic range. HDR has no highlight roll-off whatsoever. If we want to emulate the film look, rolling off highlights is a necessary evil. How highlights roll off is a critical creative decision, significantly impacting color and texture and consequently the feel of materials (metal, water, skin), light sources, and atmosphere. 

Highlight Roll-Off: Best Practices

Deciding how much highlight roll off to apply is a balancing act between preserving artistic intent and maintaining detail and texture. Choosing the amount of highlight roll-off that works best for the project, then tailoring it to each scene using tools like contrast/pivot, custom curves and power windows is a good strategy.

“The important thing with film and HDR is maintaining the highlight roll-off and making it feel filmic, because one thing that HDR does enhance, is it can make your grain a lot more apparent in a way that’s not very attractive, especially as you push in the highlights, because you just have so much more highlight range now that in your scans, you’re just kind of stretching the contrast of the top end of your image. So, being mindful of your highlight roll-off is the most important thing. I mean, that’s just general with HDR and making it feel appealing, but with film especially, because your grain can start looking noisy and a little gross.” – Matt Wallach, Senior Colorist, Company 3. Working With Film Scans For HDR Deliverables. DeMystify Colorgrading.

The perils of applying excessive highlight roll-off:

• Erodes contours, destroying the volume of shapes and surfaces
• Tosses out texture and detail
• The image becomes flat
• Lessens the impact of specular highlights that are requisite for HDR
• Impacts colors, making them less saturated.
• Image resembles SDR

The advantages of applying an appropriate amount of highlight roll-off:

• Flattering to faces, more forgiving of imperfections
• Decreases perceived sharpness that persons of discernment find objectionable
• Fewer hotspots, minimizing the number of power windows required
• Suppresses noise
• Lower contrast reduces the intrusion of judder that is aggravated by today’s high contrast, high luminance displays
• It’s a key component to achieving the analogue film look

Budgeting For Highlights

While in SDR, “highlights” might be ~ 2.7X diffuse white, in HDR, highlights can be as high as 10X diffuse white:

“In traditional imaging, the range allocated to these highlights [specular highlights and emissives] was fairly low and the majority of the image range was allocated to the diffuse reflective regions of objects. For example, in hardcopy print the highlights would be 1.1x higher luminance than the diffuse white maximum. In traditional video, the highlights were generally set to be no higher than 1.25x the diffuse white. Of the various display applications, cinema allocated the highest range to the highlights, up to 2.7x the diffuse white.” – source

Diffuse White, Headroom & Separation 

Leaving little headroom (i.e. a higher value) means brighter diffuse whites at the expense of flatter looking specular highlights, while leaving more headroom allows for better looking highlights.

“A High Dynamic Range System (HDR System) is specified and designed for capturing, processing, and reproducing a scene, conveying the full range of perceptible shadow and highlight detail, with sufficient precision and acceptable artifacts, including sufficient separation of diffuse white and specular highlights.” [italics added] SMPTE

Diffuse White Level Not Fixed

The majority of HDR narrative work has a diffuse white level much lower than that recommended by the ITU and it’s a constantly shifting target. This may frustrate those desperate for hard and fast rules, but this approach has a number of advantages, not least of which is that it accords the colorist considerable artistic freedom to set aside that additional reserve for individual scenes to powerful dramatic effect.

Neil Robinson, formerly Senior Director, Strategic Projects at LG Electronics (currently at Apple), confirmed that most theatrical and episodic content takes a much more conservative approach toward diffuse white than that established by the ITU, writing that despite “ITU recommendations, most theatrical and episodic HDR content does not have a diffuse white level of 203 nits. The diffuse white level in such content usually changes from scene to scene, and is far closer to the typical diffuse white level of SDR content of between 80 and 100 nits at most.”