Understanding HLG and Instant HDR Workflows

As if there weren’t enough acronyms and phrases in the photo and video industry, Hybrid-Log Gamma (HLG) and High Dynamic Range (HDR) are probably ones that you should take care to learn more about, because they are going to become more important in the coming months and years. If you follow photography and video news, you may have heard these terms thrown around, most notably with the introduction of the Sony a7R III and Panasonic GH5S, two mirrorless cameras that have stellar video quality. Both offer HLG as a setting and mention it as a means for achieving “instant HDR,” and it is extremely likely that future cameras will offer the same function because HDR is here to stay.

For those of you who don’t know about HDR or immediately think of over-processed landscapes, you should be pleased that the current HDR relates to image processing for televisions and displays, allowing them to produce a wider range of colors and contrast, resulting in more vibrant and true-to-life images. It really is breathtaking and, if you haven’t seen an HDR display and compared it to a standard dynamic range (SDR) screen, you should walk into the B&H SuperStore and check it out. The colors pop, the contrast ratios are incredible with rich, deep blacks and powerful, eye-catching highlights, and if you have been delaying on upgrading to 4K because you can’t really see this difference, this will change your mind.

Professionals and advanced amateurs who are in tune with the latest advancements in display tech may be aware and excited to use HDR in their own projects. However, if you have considered mastering your own HDR movies at home, you may have found it is nowhere near as simple as it seems. Professional grading requires HDR-capable displays that cost tens of thousands of dollars, though it is possible to throw together a makeshift theater with an off-the-shelf TV if you are determined. On the other hand, HLG makes it possible to record a video and then immediately play it back with extended dynamic range and a wider color gamut on current compatible TVs.

Hybrid-Log Gamma was developed jointly by BBC and NHK, two giants in the television broadcasting industry. They set out to solve a problem of compatibility with HDR content and non-HDR displays, and so HLG was born. This unique setup allows the footage to play normally on either an SDR or HDR set, thanks to relying on information stored in the TV, as opposed to highly particular metadata that is used for HDR10, HDR10+, and Dolby Vision. Obviously, this is a dramatically oversimplified explanation, but for shooting you don’t really need to know all the differences—just that this is the easiest/only one to work with in-camera now, and one that is seemingly gaining support online from YouTube and other services.

With the setting on your camera, you can now flag your footage as HDR, and if you plug in said camera to a 4K TV with HLG HDR support, it will immediately play it back with the appropriate contrast and tones, including the brighter highlights and increased contrast that make HDR so appealing. This ability is also what makes this an “instant” HDR workflow. It is able to do this by adding metadata that applies a logarithmic curve and additional color information on top of what is normally an SDR signal, allowing for greater brightness and a wider gamut, and theoretically better-looking footage.

Many of the more experienced filmmakers out there may be thinking, “But what about my S-Log3 and V-Log L profiles?” Those are still going to come in handy for professional workflows where you are going to be editing and coloring the footage in post, to get improved colors and enhanced control over the brightness and contrast of each scene. HLG, unfortunately, doesn’t work too well once you start putting it through a normal post-production process because the metadata and flags will tend to get lost or changed. If you really want to maximize the full potential of your footage, a true HDR workflow ending in HDR10 or Dolby Vision is, at the moment, still the best practice, especially if your target is a distribution in theaters or on VOD services.

While this is being billed as an “instant” HDR workflow, you should have certain pieces in place before it works the way it is intended. The primary need is to have a 4K HDR TV set up that currently supports HLG, which isn’t the easiest thing yet. HLG is being added to many current TVs via firmware updates, but if your display is a couple of years old, you will likely need to upgrade to get full compatibility. I would recommend something like LG’s C7P-Series OLED TVs or Sony’s upcoming A8F sets, if you are out shopping now, but be on the lookout for many more displays and even computer monitors to come out with native support.

Realistically, the current uses for this are limited to home movies or projects with fast turnarounds and little to no editing required. For example, if you were covering a live event and had a static shot to throw up online afterwards, this would work brilliantly. Also, early reports from users of the cameras think that the color and contrast of the HLG profile is easier to use in post than traditional log gammas, so this is something else to consider before you go out to your next shoot. In any case, HLG HDR being made available in the a7R III and GH5S is a wonderful start and, hopefully, we can enjoy HDR on all of our devices in the future.

Are you excited to use HDR on your next project? Do you have any questions about how you can do this at home? Sound off in the Comments section, below!