HDR: Projector Compatibilty Issues
November 16, 2016,
With HDR (High Dynamic Range) video sources and HDR-capable projectors now both available, it is certain that HDR and UHD resolution can take picture quality up a significant step. However, at the moment HDR is very much bleeding edge, and compatibility problems between sources and displays abound. The industry will eventually work out the kinks, and everything will work together seamlessly without you having to know any details. For now, however, here are some tips on how to navigate the HDR landscape.
First, let's look at important HDR standards, specifications, and guidelines:
The oversimplification you'll see most often is that there are two HDR standards that you need to match between the video source and display--HDR10 and Dolby Vision--with the assumption that if both support the same one, they'll work together. The reality is that:
1. Dolby Vision, once again, is irrelevant for projectors. There are no models currently supporting it or on the near horizon, and
HDR Color definitions
Color depth: Also known as bit depth, color depth refers to the number of bits used to define the levels of each of the three color components, Red, Green, and Blue, in a pixel. 8-bit color is common. This is also confusingly referred to as 24-bit color because a pixel is defined by three color components. (8 bits per color times 3 colors equals 24 bits per pixel). A little arithmetic will reveal that 2 to the 8th power gives you 256 different potential values for each R, G, and B component, and 256 x 256 x 256 gives you the 16.7 million colors you hear advertised all the time. So 8-bit color depth equals 16.7 million colors.
We now have the option for deeper color systems using 10-bits or 12-bits per color. By the same logic, these can also be referred to as 30-bits and 36-bits per pixel.
HDR10 color depth: The HDR10 definition specifies 10 bits per color. Some HDR10-compatible devices also support 12 bits per color, which HDMI 2.0 and 2.0a (which adds HDR support) have the bandwidth to handle. However, 12-bit color isn't part of the HDR10 definition.
What HDR? Get a dark room. With projectors, HDR of any variety works best when viewing at night or in a dark room. HDR can give you blacker blacks and more brilliant highlights than SDR for a wider tonal range. However, to see the difference on a projector you must be viewing in a very dark room. Even a small amount of ambient or reflected light will compromise black levels, reduce contrast ratio, and hide much of the difference between HDR and SDR. It doesn't take much light to do that, so to get the full visual benefit, you'll want the viewing space as close to a black hole as possible.
As with any newl standards, manufacturers can interpret the details of HDR10 differently. This can lead to outright incompatibilities between products or just make it a little harder to get them working together than it should be. Fortunately, there are only a handful of HDR-capable projectors, UHD Blu-ray players, and game consoles available--or soon to be available--at this writing, which makes it easy to compile a list of what works with what. The information presented here is based on testing results reported by Epson, JVC, and Sony.
One type of HDR source material that has not been thoroughly tested is streaming video from Netflix, Amazon, and Sony Ultra, all of which support HDR10 with UHD. (VUDU limits itself to Dolby Vision only). The problem is that 4K HDR compatibility testing with streaming sources is complicated by the extra hardware that connects the source to the projector. A projector might show a 4K HDR signal from Netflix through one device but not through another. So compatibility testing with streaming sources is a lot more complicated than testing with Blu-ray players or game consoles that interface directly to the projector. In short, if 4K HDR is on the bleeding edge, streaming 4K HDR is on the leading edge of the bleeding edge.
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