You may know that "HDR" stands for High Dynamic Range, a term with origins in photography. Now, it's a buzzword that's popping up on more mobile displays and is being touted as a selling point. What exactly does HDR mean for tablets, phones and laptops?
HDR in photography and displays are two different but loosely related designations. It is helpful to know the phrase's basis in photography, to help establish some of the terminology used. The "dynamic range" of an image refers to the contrast between the darkest parts of the image (the shadows) and its lightest parts (the highlights).
In photography, an HDR image has a higher amount of contrast than a normal capture: Its highlights are lighter and/or its shadows are darker. HDR is good because normal human vision can perceive a greater range of colors and brightness than a camera can, so a higher dynamic range better mimics the real-life viewing experience. Most quality smartphone cameras have an HDR mode that combines multiple exposures of the same image. That way, all of the shadows, highlights and midtones have as many tones as possible.
On a display, HDR has a different meaning. An HDR designation on a display means that it can produce lighter lights, darker darks and by extension, a larger range of colors, with variations in brightness and an amount of contrast that's closer to what we see in real life. Ordinarily, the pixels on a display (if lit) have fairly equal brightness, but HDR allows more variation.
HDR televisions have been around for a few years now, but mobile HDR displays are just starting to emerge. Samsung has spearheaded this effort: The ill-fated Note 7 was one of the first phones to claim an HDR display, and the new Galaxy Tab S3 tablet has followed suit. The Sony XZ Premium smartphone also boasts an HDR display, as does the LG G6. Does an HDR display have better quality? Yes, but it's difficult to quantify the amount of improvement.
First of all, you'll need HDR content for a true HDR experience, even with the right display. Ordinary video formats don't contain enough information to be able to fully utilize the greater contrast ratio that HDR provides. Netflix, Amazon and Hulu all offer HDR content, but titles are limited and they usually require some hunting down and/or a higher cost.
Secondly, the crop of mobile devices boasting HDR displays have been using different standards for what exactly qualifies as high dynamic range. The LG G6, for example, supports HDR10, an open standard that has been adapted by many TV manufacturers. But Samsung hasn't specified the HDR standard on the Galaxy Tab S3 and the Sony XZ Premium also seems to have self-imposed criteria for HDR.
There's also Dolby Vision, a proprietary designation that often pops up in HDR discussions. In the TV world, there are more specified hardware and software requirements for Dolby Vision, but on a mobile device, it's largely software-based. According to Dolby, the software works with individual phone displays – regardless of resolution or frame rate – to continually optimize and expand color range and brightness. So far, the LG G6 is the only smartphone with Dolby Vision, but we expect this to change.
Hopefully this confusing situation of varying standards will improve in light of a benchmark recently established by the UHD Alliance, a group of entertainment, electronics and technology companies that work to establish common standards for display certifications. At the Mobile World Congress last month, the UHD Alliance unveiled the "Mobile HDR Premium" specification, which defines resolution, dynamic range, color space and bit depth requirements for smartphones, tablets and laptops.
In the future, if a display is Mobile HDR Premium certified, you'll know it meets a certain set of requirements. However, manufacturers are not compelled to abide by UHD Alliance standards, so to be realistic, it's unlikely that the format wars will be over anytime soon.
Though it's wise to approach non-standardized HDR claims skeptically, dynamic range is still a very important aspect of display quality. If you were to view the same content on two displays of equal resolution, one with HDR and one without, you'd very likely find that HDR provides a more attractive, realistic viewing experience. It's just difficult to quantify how much better it is. And if you're not viewing HDR content, it's likely you'll never miss it.
