High dynamic range (HDR) video is one of the newest TV feature bullet points. It can push video content past the (now non-existent) limitations to which broadcast and other media standards have adhered to for decades. But adoption could be slow over the next few years because it's a complicated and somewhat esoteric feature. Let us explain.
Standard Dynamic Range
TV contrast is the difference between how dark and bright it can get. Dynamic range describes the extremes in that difference, and how much detail can be shown in between. Essentially, dynamic range is display contrast, and HDR represents broadening that contrast. However, just expanding the range between bright and dark is insufficient to improve a picture's detail. Whether a panel can reach 100 cd/m2 (relatively dim) or 500 cd/m2 (incredibly bright), and whether its black levels are 0.1 (washed out, nearly gray) or 0.005 (incredibly dark), it can ultimately only show so much information based on the signal it's receiving.
Current popular video formats, including broadcast television and Blu-ray discs, are limited by standards built around the physical boundaries presented by older technologies. Black is set to only so black, because as Christopher Guest eloquently wrote, "it could get none more black." Similarly, white could only get so bright within the limitations of display technology. Now, with organic LED (OLED) and local dimming LED backlighting systems on newer LCD panels, that range is increasing. They can reach further extremes, but video formats can't take advantage of it. Only so much information is presented in the signal, and a TV capable of reaching beyond those limits still has to stretch and work with the information present.
What Is HDR?
That's where HDR video comes in. It removes the limitations presented by older video signals and provides information about brightness and color across a much wider range. HDR-capable displays can read that information and show an image built from a wider gamut of color and brightness. Besides the wider range, HDR video simply contains more data to describe more steps in between the extremes. This means that very bright objects and very dark objects on the same screen can be shown very bright and very dark if the display supports it, with all of the necessary steps in between described in the signal and not synthesized by the image processor.
To put it more simply, HDR content on HDR-compatible TVs can get brighter and darker at the same time, and show more shades of gray in between. Similarly, they can produce deeper and more vivid reds, greens, and blues, and show more shades in between. Deep shadows aren't simply black voids; more details can be seen in the darkness, while the picture stays very dark. Bright shots aren't simply sunny, vivid pictures; fine details in the brightest surfaces remain clear. Vivid objects aren't simply saturated; more shades of colors can be seen.
This requires much more data, and like ultra high-definition video, current optical media can't handle it. Blu-ray discs cannot hold HDR information. That will change over the next few years as the UHD Alliance pushes the Ultra HD Blu-ray standard. It's a disc type that can hold more data, and is built to contain 4K video, HDR video, and even object-based surround sound like Dolby Atmos. It could solve all of the distribution problems of 4K and HDR without requiring a very fast Internet connection. Online streaming can also offer 4K and HDR video, but Ultra HD Blu-ray provides a physical and broadly accessible way to get it.
What You'll Need
Don't expect to use these discs with your existing Blu-ray player, though. While they're still called Blu-rays, they use different technology and different encoding standards to stuff all of that information onto the medium, and you'll need an Ultra HD Blu-ray player. They're still pretty rare at the moment, with only a few options currently available, like the pricey Samsung UBD-K8500 and the Microsoft Xbox One S game system.
If you don't want to deal with physical media, HDR content is trickling steadily onto streaming services like Netflix and Vudu. Of course, like any 4K content, HDR depends on having a very fast, reliable Internet connection. If your stream can't support it, you won't be able to watch your desired movie or show in HDR even if it is available.
You'll need an HDR-compatible TV, as well. HDR is not 4K. A 4K screen might support HDR, but that doesn't apply to all sets. If your TV doesn't support HDR, it won't take advantage of the additional information in the signal, and the panel isn't calibrated to handle that information even if it was properly read. Even if the TV can handle the signal, it might not produce a particularly better picture (our reviews of HDR-capable TVs include evaluating HDR performance), particularly if it's a less-expensive LED TV. So, if you haven't picked up a 4K television yet, you might want to wait for a good HDR-compatible one that fits your needs in the future. If you have, don't fret; HDR content is even less abundant than 4K video, and we won't see it become widely available for a while.
Types of HDR
HDR isn't quite a universal format, and currently HDR content is split into two groups: HDR10 and Dolby Vision. HDR10 is the standard pushed by the UHD Alliance. It's a technical standard with specific, defined ranges and specifications that must be met for content and displays to qualify as using it. HDR content available on Ultra HD Blu-ray discs are generally HDR10. Televisions that support HDR10 are allowed to display the UHD Alliance's Ultra HD Premium logo.
Dolby Vision is Dolby's own HDR format. While Dolby requires certification for media and screens to say they're Dolby Vision compatible, it's less of a distinct standard than HDR10. Dolby Vision, like HDR10, contains much more information about light and color for each pixel. However, Dolby Vision media is calibrated to fit the profiles of individual Dolby Vision displays to produce the best picture based on each panel or projector's limitations and range. The end result is still a picture that has wider, more varied colors than standard dynamic range video. Dolby Vision-compatible televisions will have the Dolby Vision logo on their packaging.
As for which HDR format is better, it simply isn't clear yet. Both can offer significant improvements over standard dynamic range, and currently both are seeing media and televisions coming out in their respective standards. Like the clash between Blu-ray and HD-DVD when high-definition video became prominent, we'll have to see which format, if either, gets a strong foothold in the market.
Where Is It Now?
Ultra HD Blu-ray discs have been trickling into stores, and major studio releases have been coming out in combination Ultra HD + Blu-ray packs that include films on both Ultra HD and standard Blu-ray discs. It's a welcome stopgap measure as Ultra HD Blu-ray players get adopted, offering an option for consumers to watch movies on regular Blu-ray until they're ready to upgrade. Not every Ultra HD Blu-ray film has HDR content, but HDR releases have prominent HDR logos on the front for easy identification.
HDR-capable televisions are still fairly rare, and limited to most manufacturers' high-end lines. The OLED-based LG Signature OLED65B6P stands out as the most prominent HDR television we've tested so far. Other HDR-capable TVs include the 2016 versions of Samsung's SUHD, Sony's XBR, and Vizio's P and Reference lines.
As for streaming, Netflix recently launched HDR support, and you can watch certain releases like Marco Polo in HDR if your television supports it and your Internet connection is fast enough. Vudu also offers HDR films on demand, and we're sure to see support expand in the future.
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