A Closer look at what HDR in 4K TVs really means
Stephan Jukic – October 05, 2015
We talk about high dynamic range, also known as HDR, here at 4K.com and with good reason, since it has become one of the major pieces of technology lingo when it comes to talking about 4K UHD TVs in recent months.
For starters, HDR has become one of the crucial technologies in the so-called quest for next-generation 4K content, which is supposed to (and quite honestly does) deliver a superior level of picture quality to even that of the first generations of 4K ultra HD video on LED/LCD displays. This development of HDR for TVs and content has manifested itself in the manufacturing of TVs with the expanded dynamic range of display contrast between brightest bright and darkest dark makes up display-end HDR.
This has been done so that said TVs can essentially more closely deliver the realism of real-world viewing by displaying content with high dynamic range encoded into it in a way that’s not possible with ordinary 4K or HD TVs.
All of this basically describes what we can call TV HDR –the Display and content side of high dynamic range. In essence, this type of HDR revolves around a display process.
The other type of HDR is that which exists in cameras themselves and this form of high dynamic range is a capture process, one in which a bunch of photo stills of a given scene are combined together to create a sort of realism that’s superior to what would be possible with a single simple take.
However, in contrast to the HDR of display technology, camera HDR doesn’t actually involve expanding the ranges of brightness themselves. It simply consists of joining together multiple exposures of a shot for a much better balance of clarity and detail in both light and dark areas of an image or video still.
Now, we’re going to go into more detail about TV HDR in particular but first, a quick bit of elaboration on high dynamic range as a general concept itself:
What is HDR?
High dynamic range, whether it is a capture process or a display process essentially involves three key things being created: First, a much broader amount of difference between the brightest bright spots and the darkest dark on a screen or in a photo, second, a much greater range of dark and bright levels between these two extremes of bright and dark, and third a high degree of precision in how and where all these different shades of bright and dark are applied to photos or displayed video.
The ultimate aim of all these core characteristics of HDR is the creation of an image that’s more realistic, or more in line with how something would look if you were actually seeing it with your eyes, in person.
Furthermore, this process of expanding or turbocharging dynamic range is being applied to display devices (mainly 4K TVs), the digitized content that gets shown on said display devices and in the cameras that are used to capture film or video.
Overall, HDR is part of the evolution towards superior, more realistic and more vibrant next generation content, most of which also happens to be in native 4K resolution.
HDR for 4K ultra HD TVs
With HDR in TVs, the fundamental concerns that manufacturers who want to create a real visual impact worry about aren’t simply about maximizing brightness and increasing darkness, they’re also about creating the most detailed possible range and precision of dark to bright spots in a piece of display content.
With this in mind, HDR-capable 4K TVs (because they’re almost exclusively also 4K TVs) work at creating a maximum amount of specific deeply dark local dimming zones for darker tones and high overall brightness where dimming isn’t activated. With the best LED 4K TVs, the resulting HDR effect can be truly impressive.
However, at least currently, the absolute master televisions for what is in effect an ideal HDR-effect are OLED 4K TVs, which currently aren’t even formally considered HDR TVs. These televisions, manufactured exclusively by LG until recently and now Panasonic as well, create superb, arguably unmatchable HDR-like effects because they can create perfect, total darkness with complete shutoff of internal screen light and deliver this or its opposite of variable brightness right down to the level of a single screen pixel, one of over 8 million that a 4K TV screen will have on it. Thus, you can imagine just how fantastically precise their level of localized dimming or brightening can be.
On the other hand, select models of these OLED TVs have only recently been updated as HDR TVs because they previously didn’t have the actual internal firmware capacity to correctly read and interpret content that has been encoded with high dynamic range, from sources like Amazon Prime or Netflix, among others that are being developed. Now, they do have this capacity thanks to the most recent firmware updates from LG and this is further augmented by their native OLED characteristics of perfect black and thus in effect infinite contrast.
Thus, we get an interesting situation in which the best levels of dynamic range and lighting precision come from a series of what were until recently non-HDR TVs while formally HDR-enabled 4K TVs can’t quite match that same OLED screen lighting precision or contrast levels. Why? Because in contrast to OLED, even the best LED TVs with the most precise level of local dimming can’t quite match the same level of perfect light emission and dark control that OLED TVs manage when they activate or deactivate their organic light emitting diodes completely with the perfect precision of a single pixel.
The Content side of High Dynamic Range
Of course, HDR for TV isn’t just about 4K TVs themselves. It’s also got its fundamental content aspect in the form of video streams and hard media content with HDR metadata encoded into it, as a sort of range enhancement instruction for TVs capable of reading and displaying a given piece of content’s dynamic range enhancement.
Sources of HDR-encoded content include Amazon Prime Instant Video, Netflix and the upcoming 4K Blu-ray media players and discs we’re all expecting to finally show up on the home entertainment scene by the end of 2015.
Furthermore, there are several competing standards of HDR dynamic range being developed, from players like the newly founded UHD Alliance, which includes Netflix, Disney, and Fox, or Dolby Vision, which is partnering with companies like Sony, Toshiba and Philips for its own version of UHD. None of these players have yet formally agreed for an across-the-board standardized version of HDR and this is affecting the technology’s implementation in TVs themselves. Though we are seeing forward movement on this with developments like the UHD Alliance’s acceptance of Dolby’s HDR spcs as an option for future devices that come out from the manufacturers working with the Alliance.
This in fact is why HDR is rarely named by manufacturers themselves when one of their HDR-capable TVs is being promoted. Companies like Sony, LG and Samsung all have their HDR-capable models but only mention the technology by its technical name in their promotional materials and not their formal TV specs.
In essence high dynamic range for TVs, digital TV content and possibly other display devices is still very much in its baby stages and nobody really knows how it’s going to develop or which formal standards will be adopted and cemented throughout the industry. What we do know however, is that this new technology that’s aimed at a much better viewing experience already creates content that looks genuinely stunning and that the Wow-factor of HDR is only going to get better from now on as high dynamic range truly improves and matures.
Story by 4k.com