TV manufacturers have found that one of the most reliable ways to get consumers to buy a new TV is to push more pixels. The big jump was from Standard Definition (480 vertical lines displayed using interlaced scanning) to High Definition (1080 vertical lines displayed using progressive scanning). Today, we're being pushed to buy "4K" TVs, but that definition switches the emphasis from vertical lines of resolution (there are 2160 of those) to the spec's horizontal pixels (3840), because that number is so much bigger than 1080.

Recently, however, an entirely new buzzword has entered the manufacturer's vocabulary: High Dynamic Range (HDR). Suddenly the discussion isn't just about more pixels, but better pixels. At its most basic, HDR delivers greater contrast between light and dark areas of a video image. How does that work and how important will it end being to your TV enjoyment? I shall endeavor to enlighten you.

How HDR works

If you’re familiar with High Dynamic Range at all, it’s likely via a setting on your smartphone or digital camera. As its name implies, the feature increases the dynamic range—the ratio of light to dark—in your photographs. It accomplishes this by photographing the subject three times at different exposures, doubling the light in each picture. The three images are then blended into one (in a program such as Photoshop, if the device doesn’t handle it internally) that retains the darkest and brightest parts from the first and third exposure, respectively. The result should be a brighter, more detailed picture that’s much closer to what your eye sees.

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The idea behind HDR video is similar: It increases the range of brightness in an image to boost the contrast between the lightest lights and the darkest darks. If you’re having difficulty grasping how that translates into a more realistic image on your screen, think of the subtle tonal gradations a fine artist creates in a charcoal drawing to build the illusion of volume, mass, and texture, and you should begin to get the picture. But HDR doesn’t just improve grayscale; its greater luminance range opens up a video’s color palette as well. “Basically, it’s blacker blacks, whiter whites, and higher brightness and contrast levels for colors across the spectrum,” says Glenn Hower, a research analyst at Parks Associates.

The result is richer, more lifelike video images. Rather than washing out to white, as it would in conventional video, a ray of sunlight reflecting off a lake in HDR will gleam, and a bright cloud will appear soft and cottony. Basically any image your current TV would render shadowed, dull, muddy, or bleached out will look nuanced, vibrant, and strikingly realistic in HDR.

The nit-y gritty on HDR TVs

Given the fervor with which TV manufacturers have chased after a more immersive viewing experience, it’s no surprise so many of them have embraced HDR. Sony, LG, Samsung, Phillips, Panasonic, and Vizio, have all promised to bring HDR-capable TVs to market this year, apparently banking on HDR to be the “killer app” that finally gets consumers to upgrade to UHD TVs.

And you will need to upgrade if you want to take advantage of HDR—the increased luminance is too much for the brightness limitations of current TVs. The amount of light a TV puts out is measured in nits. Most current TVs have a peak brightness around 400 nits. To display the increased range of brightness an HDR video captures, you need a peak closer to double that. The HDR-equipped TVs by the above brands max out anywhere from 700 to 1000 nits, indicating some of them believe in brighter brights than others.

Sony’s 65-inch x930c is one of several HDR-equipped 4K TVs to hit store shelves this year.

That brings up a significant issue. Currently there’s no standard for HDR, so it’s a bit of a free-for-all with each manufacturer offering their own take on the technology. Samsung labels its HDR implementation “Peak Illuminator Ultimate,” while LG calls its “Ultra Luminance” and Panasonic offers “Dynamic Range Remaster.” Sony offers two flavors of HDR—“X-tended Dynamic Range” and “X-tended Dynamic Range Pro.” And Vizio, Sharp, and TCL are throwing their hats in with Dolby’s HDR tech, “Dolby Vision.” If that doesn’t lay the groundwork for enough consumer confusion, the lack of a standard leaves the door wide open for a manufacturer to slap “HDR” on its TVs just because they’re bright, whether or not they can truly handle HDR content.

Fortunately, the recently formed UHD Alliance is hard at work on developing a stronger definition of what qualifies as “Ultra HD,” including HDR requirements, so with a little luck we may have a standard before the end of the year.

The content question

Even regular video will look better on an HDR-equipped TV, but to get that pop-off-the-screen realism, you need content produced with high dynamic range. The good news is it’s coming.

Warner Bros. and Dolby have announced that “The Lego Movie,” “Edge of Tomorrow,” and “Into the Storm” will be remastered in HDR this year, but they’ll only be available via streaming to Dolby Vision-enabled TVs. Amazon will bring HDR versions of its original content to its Prime Instant Video service later this year, and Netflix will similarly make its original programming available in HDR. (According to the streaming giant, an HDR stream will only add about 2.5Mbps to a user’s bandwidth requirements.) And given that the Blu-Ray Disc Association’s updated Ultra HD Blu-ray format includes HDR support and is expected to start rolling out later this year, film studios’ back catalogs also seem ripe for re-color-grading for HDR. Whether altering older content will irk filmmakers and fans the way colorization did in the 1980s remains to be seen.

Amazon will bring HDR versions of its original content to its Prime Instant Video service later this year.

Broadcast HDR content however, is likely to lag behind. The U.S. broadcast system isn’t currently set up for 4K, much less HDR, but there’s really no incentive to update it until there are HDR-equipped TVs in enough homes to justify the equipment upgrade.

What it means for you

Buying into a new technology is always dicey, and HDR is no exception. Upgrading your TV when HDR models hit the shelves won’t be cheap—for reference, Sony’s 65-inch X930C, which seems to be the first out of the gate, retails for $4500—but there are no known connectivity or other compatibility issues that would require you to overhaul the rest of your home theater.

As with 4K before it, the decision on when to upgrade comes down to content. Sure, there looks to be enough coming down the pipe to make it enticing, but until a major studio either starts producing multiple HDR titles a year or offers a decent portion of its library to be remastered in HDR, it will be tough to justify the expense.

If you do decide to take the plunge before an HDR standard is formalized, buyer beware. Do your research and stick with the bigger brands to avoid ending up with a TV that isn’t really HDR ready.

There’s no harm in waiting, either. As we said earlier, Ultra HD is a puzzle, and though HDR fills it out more, there are still other pieces such as color gamut and bit depth that have yet to be placed. Give it a little more time, and the Ultra HD picture may become even clearer.

Editor's note: This article was updated to correctly report the difference between vertical resolution and horizontal pixels.