What is HDR? Why HDR will improve your movie watching
The TV industry never stands still, with new technologies appearing every year to improve TVs and convince you that now’s the time to upgrade.
Over the past few years we’ve seen the move from CRT to thin TVs, we’ve seen the rise and fall of plasma, we’ve witnessed the ascent of HD, Full HD and Ultra HD, we’ve seen dalliance with 3D and the debate around curved or flat. Joining this race is HDR, the latest technology that’s among the acronym-laden features on new TVs – and it’s a tech that’s growing.
HDR hit the big time in 2017, throwing up a range of HDR formats, lots of HDR devices and more HDR choices to make. That’s continued through recent years, with HDR becoming more accessible across a full range of devices and services.
What is HDR?
HDR stands for high dynamic range. The abbreviation will be familiar because it’s a term also used in photography, with HDR on some cameras and many smartphones: it’s a feature on the iPhone, for example.
It’s the same thing, because on televisions, just as in photography, the aim is to recreate an image that’s closer to that seen by the human eye, or to better recreate the vision of the original storyteller. That often means balancing out light and dark areas or the range of colours, and not losing, for example, shadow detail because of a bright sky.
When it comes to TVs, this is handled in a couple of areas. The first is contrast, dealing specifically with the relationship between light and dark, and colour, with HDR offering a wider range of colours, particularly in challenging situations like sunsets.
The results delivered by HDR should mean more sumptuous colours, bringing more realism and depth, and added “pop”. HDR aims to be a visual treat, which it very much is. HDR preserves the gradation from dark to light in ways that SDR (standard dynamic range) cannot. That results in fidelity in the darkness, as well as that very bright point of light, with both being rendered with lots of detail and colour.
The “original storyteller” aspect is also important, as HDR is very much being pitched as bringing the director’s vision to your TV, much like Hi-Res music claims to be bringing the artist to your ears. In the case of HDR, this could extend beyond the realistic into more radically styled visuals. In previous standards, including those used on Blu-ray, it just wasn’t possible to achieve the same results.
What are the HDR tech specs?
HDR uses panel technology deliver this wider colour range and contrast, and it’s very much about brightness and illumination. To view HDR content, you need to have a display that’s compatible with HDR, it’s as simple as that – and for many that will be a television, although in recent years laptops, tablets and phones have all offered HDR too.
HDR-capable sets are suped-up televisions. Many HDR sets have a backlight system that can output about 1,000 nits peak brightness or greater, whereas standard TVs typically only output 100 nits, which is the level that Blu-ray and standard TV content is specified to.
Nits refers to the brightness, although this isn’t used uniformly when watching HDR content – this only refers to brightness in particular places, those highlights in a scene. Using an increased brightness range and a wider colour gamut, HDR can recreate visuals that weren’t previously possible.
However this isn’t about absolute brightness, it’s about the range, so although you’ll see some LCD manufacturers talking about 1000 nit brightness, others, like OLED manufacturers, might be offering 800 nits. Because both offer the wide range between dark and light, they both have that ability to carry the HDR label.
When it comes to colour standards, HD TVs offer an 8-bit video specification known as Rec. 709, or BT.709. HDR steps up to 10- or 12-bit Rec. 2020, or BT.2020, which represents 60 times more colour combinations with smoother shade gradations. Those numbers don’t really mean anything in themselves, they’re just the standard defined by the ITU (International Telecommunications Union) but you’ll often hear TV manufacturers saying that they conform to BT.2020, for example.
To help complicate things, HDR was initially introduced with Ultra HD (4K). HDR is included in the Ultra HD Blu-ray spec, and the UHD Alliance created a certification called Ultra HD Premium, which confirms that a device (e.g., TV or Blu-ray player) meets particular standards for Ultra HD and HDR, although in the years since the launch of the Ultra HD Premium badge, it’s hard to see that it actually drives TV sales, because not everyone uses it.
However HDR isn’t linked to resolution, so there are HDR capable TVs that are full HD (1080p rather than 2160p), just as there are phones and tablets with HDR displays at a wide range of resolutions.
Things don’t stop there either. Aside from those ITU specifications for devices, there are a number of standards for HDR content that are being talked about: HDR10 and Dolby Vision are the more established technologies, HLG and Advanced HDR by Technicolor are emerging technologies, while HDR10+ wants to turn the whole thing on its head. More recently, Vesa DisplayHDR has emerged as a standard specifically aimed at the PC monitor market.
That might all sound confusing, but as a “consumer” there are only a few things you really need to look out for.
What HDMI cable do I need for HDR?
In terms of cables, there’s nothing special you need from your cable. If you’re watching Ultra HD Blu-ray, then an 18Gbps or High Speed HDMI cable is recommended, but unless you have really old HDMI cables, you probably have that covered already. It doesn’t have to be an expensive cable either, the Amazon Basics ones work just fine.
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The only real HDMI implication on HDR comes from the sockets themselves (and you either have them or don’t have them, you can’t upgrade the hardware on your devices) and this is a consideration when it comes to HDR passthrough on AV receivers or soundbars.
You’ll need HDMI 2.0a for HDR to be part of the signal that makes it to your TV. If you have an old soundbar or receiver that offers 4K passthrough using HDMI 1.4, the HDR part won’t make it to your TV. It might be that you have to use optical or ARC to get the sound back to your audio device and go straight from source to TV for anything you want HDR on.
If you have an Ultra HD Blu-ray player, you’ll likely find it has two HDMI connections on the rear so you can route video to the TV and audio your sound system directly to get around this. Of course, the most important thing is that your TV supports HDR – and if it does, it should have the right HDMI connection on the rear to support HDR inputs, although if you’re streaming HDR content from the TV’s own app, that doesn’t matter.
What is HDR10?
HDR10 is referred to as “generic” HDR, which is a slightly derogatory term, but HDR10 really refers to the baseline specifications for HDR content.
HDR10 is a 10-bit video stream, over 1 billion colours, and if you have HDR-compatible devices, it will support HDR10. This is included in the specification defined by the Blu-ray Disc Association for those Ultra HD Blu-rays, and it’s HDR10 support that’s included in the Ultra HD Premium certification we’ve talked about.
One of the things that HDR10 does is tell the display the content is being viewed on how bright things should be. The aim is the carry that information from the original studio monitor through to your living room.
HDR10 is also the HDR standard that the Xbox and PlayStation offers, although the Xbox Series consoles also support Dolby Vision.
Technically, it uses static metadata, i.e., it only tells the display those values once and then that applies to the whole movie.
What is Dolby Vision?
Things can never be simple, especially not in home entertainment, so there’s an alternative HDR standard and it’s called Dolby Vision.
One of the things that makes Dolby Vision different is that it’s designed as an end-to-end HDR process. So from capture through processing and into production, Dolby Vision is designed to preserve information that was originally captured and pass it on. It does this using metadata that’s then read by the Dolby Vision decoder in the TV you’re watching. The aim is to give you an HDR experience that’s closer to the original by supplying more information – it uses dynamic metadata.
That tells the display device how bright it should be, but rather than provide one value as HDR10 does, it can do this for every frame. Dolby Vision can deliver 12-bit colour depth (68 billion colours) and supports backlight systems four times more powerful than standard HDR TV sets, so Dolby Vision has been designed as future-proof, surpassing the current specifications for “generic” HDR10, even if there’s nothing you can currently buy that fulfils that potential.
But a Dolby Vision decoder doesn’t just support Dolby Vision HDR content, it will also handle HDR10, so if you have a Dolby Vision compatible device and you’re not watching Dolby Vision HDR content, there shouldn’t be a problem. However, if you don’t have the Dolby Vision decoder, you can’t take advantage of Dolby’s system.
That also applies to other devices like Apple TV 4K: these devices support Dolby Vision, but your TV will have to support it too. The same applies to Ultra HD Blu-ray players – if your TV doesn’t support Dolby Vision, you’ll be watching HDR10 instead.
Originally Dolby said that you needed to have a hardware decoder in your TV, but things have softened dramatically, with Sony updating some TVs to support Dolby Vision that previously didn’t, allowing DV support as a software solution rather than hardware. Through 2019 we saw more manufacturers move to support Dolby Vision in more affordable TVs – it’s no longer a format limited to flagship TV sets or expensive OLED models.
Dolby Vision is now also being widely touted as a format supported on mobile devices too.
What is HDR10+?
Samsung announced an open standard for HDR called HDR10+ and has used it on its TVs since 2018. It’s very much related to HDR10 that we’ve talked about above, but it makes a move to combat that dynamic metadata available from Dolby Vision.
What HDR10+ does is use dynamic metadata (basically more information) to tell the display how bright it should be. This is something that all HDR standards do, but as we’ve already discussed, HDR10 has static information, whereas Dolby Vision can set the brightness for each frame, making it more accurate. HDR10+ is also be able to deliver metadata frame by frame if needed, or scene by scene as needed by the content, so the brightness remains accurate throughout.
Here’s the business angle: Dolby Vision is a proprietary format that involves paying a license fee, so the introduction of HDR10+ as an open standard introduces a comparable format that doesn’t need that license. Often that means it is popularly adopted because it’s free to use.
Amazon Video partnered on the announcement of HDR10+ and content started appearing in December 2017 and the system has generally been growing, with 2019 seeing a number of TVs launch that support both HDR10+ and Dolby Vision, something that’s continued since then.
Finally, HDR10+ really aims to boost the performance of cheaper TVs. We’ve seen HDR10+ demos on mid-range HDR sets that don’t have the peak brightness of flagship models and the difference between HDR10 and HDR10+ is remarkable.
What is HLG?
HLG stands for hybrid log gamma, which is a system for HDR developed by the BBC and NHK. The aim of HLG is to recreate that HDR standard for broadcast, rather than streaming or via optical disc as is the case with HDR10 and Dolby Vision. Because broadcast is less consistent than those other delivery systems, the aim of HLG is to create an HDR system not dependent on metadata.
Ultimately, HLG can reproduce the HDR effect without needing special equipment to receive it or process it, which should allow a good deal of backwards compatibility, as well as being cost effective for TV production companies, as they won’t have to upgrade all their equipment.
The BBC has served HLG content available via BBC iPlayer. Starting with the stream of Blue Planet II in 4K HDR it then moved onto the Royal Wedding, Wimbledon and the World Cup in 2018. HLG is now widely supported on HDR TVs and HLG is the standard that Sky Q is using for its HDR delivery too.
What about HDR10+ Adaptive and Dolby Vision IQ?
One of the big problems with HDR content deliver is that it’s dependent on the brightness of the TV. Having outlined that HDR would set the brightness for you using metadata, many manufacturers then offered the option to have brighter to dimmer HDR, basically undercutting things.
That outlined a bigger problem which was that viewing happens in lots of different environments, with TV’s often having ambient light sensors to adapt to the surroundings. That’s where adaptations like HDR10+ Adaptive and Dolby Vision IQ come in, with both aiming to incorporate ambient light levels so that the correct presentation of the content can be delivered without it looking too bright or too dark because of the conditions the viewer is watching in.
There’s still a huge battle running between what the original producers of content think it should look like and how people like to watch things, with systems like Filmmaker Mode popping up in an attempt to deliver the director’s original vision.
What is Vesa DisplayHDR?
Moving along from TV watching, Vesa announced in late-2017 that it was introducing another standard for HDR. The justification was that, as Vesa saw it, there was no consistent standard to certify devices in the PC industry. With many monitors touting HDR support, this was designed as a transparent approach to create a comparable standard across monitors from different manufacturers. This applies to both external monitors and built-in, i.e., laptops.
There are three levels to the Vesa DisplayHDR standard:
- DisplayHDR 400 – entry-level, 8-bit, global dimming, 400cd/m2 brightness, colour boost over SDR
- DisplayHDR 600 – enthusiast level, 10-bit, local dimming, 600cd/m2 brightness, colour boost over DisplayHDR 400
- DisplayHDR 1000 – professional level, 10-bit, local dimming with 2x contrast increase over DisplayHDR 600, 1000cd/m2 brightness
A lot of manufacturers signed up and we seen certified monitosr announced about the standard: the Samsung CHG90 QLED gaming monitor was the first launch with the DisplayHDR 600 standard.
Which TVs support HDR?
You need a HDR-compatible TV to see HDR content and practically every TV manufacturer you can think of now has HDR-compatible TV sets.
Every flagship and top-tier Ultra HD (4K) or 8K televisions launched since 2016 support HDR in some form, and HDR is supported across both LCD and OLED televisions, as we’ve discussed.
It’s important to note that although Ultra HD Blu-ray includes HDR specification, straight forward Ultra HD TV doesn’t: there are some older 4K/Ultra HD televisions that have no HDR support.
This isn’t something that can be fixed with software either – if the panel isn’t capable enough, it can’t display the colours or the brightness, regardless of the resolution.
What HDR content is out now?
Netflix
Netflix offers HDR content supporting both Dolby Vision and normal HDR formats. It started showing this content with Marco Polo and a wide range of content has followed in HDR. HDR Netflix is available on consoles, streaming devices and natively through HDR TVs, although to access HDR you need to be subscribed to the top level of the service.
Amazon
Amazon announced in July 2015 that HDR content was available through its video service. It now offers episodes of its original series in HDR at no additional cost to paid Prime subscribers, such as Mozart in the Jungle or Bosch. You can access Amazon in HDR through TVs directly and via most streaming sticks and boxes.
Ultra HD Blu-ray
Ultra HD Blu-ray is obviously one of the big avenues to supply UHD and HDR content. HDR is part of the Ultra HD Blu-ray specification, so movies appearing on this new format can offer HDR.
YouTube HDR
YouTube announced support for HDR on 7 November 2016. That means Google’s video service is not only a source of 4K and 360-degree video, but also HDR. This should help give HDR a lot of exposure as there will be a free source of HDR content, but again, you need to have a display that supports it.
Apple TV and TV+
When Apple launched the Apple TV 4K it also also announced that it was upgrading a lot of movies purchased from iTunes – for no additional cost. iTunes (or Apple TV app) offers a wide variety of Dolby Vision content available to stream and it’s better value for money in many instances than rival streaming services. Of course, you’ll have to play via a device offering the Apple TV app, which is now widely available.
Vudu
Vudu supports Dolby Vision as we’ve already mentioned, so there’s support for some Vudu content in HDR using Dolby Vision. However, this is only supported on some Visio models. For more information on Vudu HDR support, see the help pages.
Google Chromecast and Play Movies
Chromecast is worth a mention, because if you have a TV that supports HDR, you’ll be able to use the Chromecast (Ultra or Chromecast with Google TV) to watch HDR content from a number of sources, including Play Movies, YouTube or Netflix.
Roku
Roku has a number of different players that support HDR. Most Roku players support HDR10, except the Roku Express. Dolby Vision is only supported on the Roku Ultra.
Amazon Fire TV Stick 4K
Amazon Fire TV Stick 4K supports HDR – including Dolby Vision – so you can plug the stick into a compatible HDR TV and enjoy content from a range of sources, including Netflix, Amazon Video and Apple TV.
HDR Gaming
Microsoft was the first off the bat with an announcement about HDR gaming, with titles like Forza Horizon 3 delivering wonderfully vibrant gaming experiences, enriched with HDR graphics. Since the Xbox One S, HDR has been available on Xbox and PlayStation, both in games in streaming services – although PlayStation doesn’t support Dolby Vision.
HDR on smartphones
One fairly untapped device for viewing HDR content is the smartphone. When Samsung launched the ill-fated Galaxy Note 7, one of the features it introduced was “Mobile HDR”. The Note 7 didn’t survive, but the new champion for mobile HDR was the LG G6, launched in early 2017. LG’s flagship smartphone supported both HDR10 and Dolby Vision and that’s something that’s continued across smartphone launches.
Many phones now support HDR and you’ll see that in some places like Netflix streaming, or through services like BT Sport, where HDR streaming was originally only available on tablets and phones, before expanding to other devices.
