High dynamic range (HDR) video is currently one of the biggest 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. It's impressive to see on TVs that can handle it, but it's also a fairly esoteric and technical feature with some variations that can lead to confusion. 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.
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.
Types of HDR
HDR isn't quite a universal format, and currently HDR content is split into two major formats: 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.
Several major streaming services like Amazon, Google Play, iTunes, Netflix, Vudu, and YouTube now support HDR for some of their 4K content. Some services use Dolby Vision for HDR, while others use HDR10. All major 4K-capable media streamers can handle HDR in some form, but not always consistently. The Apple TV 4K and Google Chromecast Ultra support HDR10 and Dolby Vision, while the Amazon Fire TV and Roku Streaming Stick+currently can only handle HDR10. And of coure there are the aforementioned UHD Blu-Ray discs.
Ultra HD Blu-ray discs have been steadily 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 are 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.
Source:PCMag
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