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What is HDR? High Dynamic Range TVs and phones explained

High Dynamic Range: Everything you need to know about the TV world’s hottest new trend, including what it means for smartphones.

It’s the feature that the best TVs boast about but why is HDR the future of TV? And what does it mean for new phones, which increasingly are getting HDR screens? Here we’ll explain all the ins and outs and answer some common questions, including:

  • What is HDR?
  • How do I know if a TV is HDR compatible?
  • What makes an HDR TV?
  • Where can I find HDR TV content?
  • What does HDR mean for phones?

What is HDR?

HDR stands for High Dynamic Range. That means a larger, more perceptible contrast between the brightest and darkest parts of an image. The idea is that your eyes can perceive whites that are brighter and blacks that are darker than traditional SDR TVs have been able to display. The introduction of HDR has changed all that.

HDR content preserves details in the darkest and brightest areas of a picture that are lost using old standards such as Rec.709. HDR10 is the standardized form of HDR that TVs and content are required to support to be HDR compatible. It’s not the only version in the market, though.  There’s Dolby Vision started by that was created by Dolby. In turn Samsung created its own version in HDR10+, which Amazon Video and a growing number of Hollywood film studios now support.

Now you know the basics, it’s worth keeping in mind that contrast and colour are the two key things to consider when thinking about HDR.

Related: what’s the best TV?

What about HDR on mobile devices? What are some of the top HDR phones?

Before we move on to exploring HDR on TVs in more detail, let’s note that screen technology tends to filter to other product categories, and so developments in the TV world have trickled down to the mobile world. Phones and tablets are increasingly bumping up their screens’ peak brightness, and there’s been a concerted effort to support the HDR-compatible versions of streaming services such as Netflix or Amazon Video.

HDR on phones won’t have the same impact or subtlety of a good TV, but it can make a big difference. It’s something to keep in mind if you’re upgrading your phone and would like to catch Star Trek Discovery, in punchy and colourful glory, on the go.

Now, back to the big show.

How do I know if a TV is HDR compatible?

The safest way is to look for the Ultra HD Premium logo. This is a stamp of approval by the UHD Alliance, a group made up of technology firms and content producers. The idea is to limit the amount of confusion when it comes to buying new kit, as chaos is easy to abuse.

Previously, HDR was rushed out to consumers before anyone had really agreed on a set of standards to define it, which led to many TVs having an HDR sticker on the box, regardless of specs or quality. TV manufacturers and content providers had very little in terms of clearly defined specs to work to when creating HDR screens and content.

With the UHD Premium label, we now know the precise, minimum specifications a TV needs to be considered truly HDR compatible.

Our guide ‘What is Ultra HD Premium?’ provides an in-depth breakdown of the logo and what it means, but read on for a condensed explanation.

That said, not all TVs that say they are ‘HDR’ have the UHD Premium certification. In these cases, you will get some of the benefit of HDR content, but these TVs won’t offer the best possible experience. The UHD Premium system isn’t perfect, but generally it’s safer to buy a UHD Premium TV.

Related: What is 4K and Ultra HD?

Ultra HD Premium

What makes an HDR TV?

There are two things that define an HDR TV. Their contrast performance and the number of colours they can display. Let’s start with the first.

Contrast: Contrast is one of the most important factors in how good a TV picture looks and it’s a key part of what makes an HDR TV. It refers to the difference between light and dark. The greater the difference, the greater the ‘contrast’.

There are two components to consider here. One is peak brightness, which rather unsurprisingly, refers to how bright a TV can go, measured in what’s known as ‘nits’. Think of one nit as the equivalent of one candle’s brightness. TVs must meet a specific number of nits in order to be given the HDR label.

The other measurement is black level. Similar to peak brightness, black level refers to how dark a TV image can appear and is also measured in nits. So, for example, a TV could have a peak brightness of 400 nits and a black level of 0.4 nits.

The difference between the peak brightness and black level is known as the contrast ratio. HDR TVs have to meet specific standards for peak brightness and black level which helps give them the dynamic appearance.

Colour: This is the second of the most important aspects of HDR. When it comes to colour, a TV must be able to process what’s known as 10-bit or ‘deep’ colour. 10-bit colour equates to a signal that includes over a billion individual colours. In comparison, Blu-ray uses 8-bit colour, which amounts to around 16 million different colours. With 10-bit colour, HDR TVs will be able to produce a vastly expanded range of colour shades, reducing overtly obvious gradations between shades. Subtle shading helps to make a scene look far more realistic.

However, as is always the case with these things, it isn’t quite as simple as this. In order to be considered HDR compatible, a TV doesn’t need to be able to display all the colours in a 10-bit signal. It just has to be able to process the signal and produce an image based on that information.

And it doesn’t stop there. If you’re still with us, there’s more colour stuff to go over. An HDR TV must be able to produce a certain amount of what’s known as ‘P3’ colour. P3 colour refers to the range of the colour spectrum which is included. The best way to think about this is imagine an overall colour spectrum, and within that a set of defined spaces. The P3 colour space is a larger than the what standard TVs use, Rec. 709, which means it covers more colours.

Colour space

Essentially, HDR means a TV can cover a wider space within the colour spectrum, and within that space, the various gradations of shades will be much smoother than on current TVs.

Related: Best 4K TVs

So, what’s HDR10+?

As mentioned, there are two competing standards when it comes to HDR: HDR10 (the dominant standard) and Dolby’s own, more advanced version, Dolby Vision. You can find out more about Dolby Vision in our guide. But now, Samsung’s own take on the technology, HDR10+ is gaining some attention, with Amazon announcing it will be supporting the standard. So, what is it?

HDR10+ is an open standard, created by Samsung and available on all the company’s 2017 TVs (it’ll be coming to 2016 models via a firmware update sometime later in 2017). It improves on HDR10 by using dynamic metadata instead of the static metadata used by HDR10. That means it can dynamically alter the brightness of individual scenes and even individual frames throughout a particular TV show or film. For example, if a scene was meant to be shown at lower brightness, HDR10+’s dynamic approach will drop the brightness level in real-time to match what the director intended.

Commenting on Amazon’s adoption of the technology, Greg Hart, Vice President of Amazon Video, worldwide added: “At Amazon, we are constantly innovating on behalf of customers and are thrilled to be the first streaming service provider to work with Samsung to make HDR10+ available on Prime Video globally later this year.”

HDR10+’s use of dynamic metadata brings it closer in line with Dolby Vision, which also uses the dynamic approach. Whether the HDR10+ will become the dominant standard is entirely unclear at this moment, but stay tuned as it seems the technology is increasing in popularity.

What’s all this OLED vs LED talk and does it affect HDR?

The two big display technologies in the AV industry are OLED and LED LCD. For a full explanation of these two approaches check out our ‘OLED vs LED LCD’ feature. In short, LED TVs use lights to illuminate the pixels in a traditional LCD screen, while the pixels in OLED displays produce their own light.

LED TVs are capable of producing high peak brightness and as such, offer the best way for manufacturers to create HDR compatible TVs. Many argue that OLED technology isn’t a great option for HDR due to its difficulties in producing a very bright image versus LCD/LED.

So how can OLED, with its brightness issues, qualify for HDR compatibility? Well, the UHD Alliance has got around the problem by introducing two standards, either of which qualifies you for UHD Premium status:

STANDARD 1: More than 1,000 nits peak brightness and less than 0.05nits black level.

STANDARD 2: More than 540 nits brightness and less than 0.0005 nits black level.

While standard one demands higher brightness and tolerates a higher black level, standard two tolerates a lower brightness and demands a lower black level. This means manufacturers looking to make LED HDR TVs, which most are, will abide by standard one, while OLED TVs will be able to gain the Ultra HD Premium label by conforming to standard two. Ultimately, it’s not about how bright you get, but how much of a jump there is between light and dark.

And that’s it. In the grand scheme of things, it won’t matter which type of TV you have as to whether it will be HDR compatible or not. LED TVs will give you an HDR image with better peak brightness but less deep blacks, whiled OLED TVs will give you an HDR image with lower peak brightness but deeper blacks.

So if I have an HDR TV, everything I watch will be in HDR?

If only it were that simple. Content has to be mastered for HDR in order to work with the standard. In other words, both the source, and the TV have to be HDR compatible. Luckily, with the advent of Ultra HD Blu-ray and advancements in online streaming from Netflix and Amazon, content creators will be able to deliver HDR content more easily.

Related: What is Ultra HD Blu-ray?

How do I start watching HDR content?

You have two options: buy a new Ultra HD Blu-ray player or stream HDR video from the likes of Netflix and Amazon. Your TV must also comply with the HDMI 2.0a standard, though any TV with the Ultra HD Premium label will do so by default.

UHD discs, with their greatly improved storage capacity, can now contain extra information which tells HDR TVs how to interpret colours and brightness levels. This metadata is not provided with standard Blu-ray discs and as a result, the picture on the TV looks somewhat different in terms of colour and brightness to how the creators intended it.

With UHD Blu-ray, the metadata can be included, allowing the disc to effectively tell the TV exactly how to display each image. That doesn’t mean that all UHD Blu-rays will be HDR – most of them are – it just means the creators now have the option of including the metadata to make the content HDR.

Related: How to find 4K HDR content on Netflix and Amazon

Ultra HD Blu-ray 9

UHD Blu-rays are now officially available in both the US and UK. All of the titles currently available come boasting the HDR logo, meaning if you have an HDR-ready TV and UHD Blu-ray player, such as the Panasonic DMP-UB900 or Oppo UDP-203, you’ll be able to watch these films in HDR.

If you’re looking to buy an Ultra HD Blu-ray player, one of the best options is the Xbox One S games console, which has a player built-in. It’s one of the cheapest players currently available, and of course also plays all the latest games on the console.

And when it comes to streaming, Netflix is making big strides. The company has previously stated that it believes adding HDR will only add around 2.5Mb/s to a consumer’s broadband requirements, versus the 12Mb/s or so of extra broadband speed you need to enjoy 4K over HD. That’s good news as it means that extra metadata can be relatively easily streamed along with the video.

Netflix now has plenty to watch in HDR. Marco Polo was the first available, but since then we’ve had Daredevil season 2 and most recently Iron Fist, plus some delicious food shows like Chef’s Table.

Rival streaming service, Amazon Prime Video, has already jumped on the HDR bandwagon, releasing season one of its original series Mozart in the Jungle in the format.

The Grand Tour, the show from former Top Gear presenters Jeremy Clarkson, Richard Hammond and James May, is also available in 4K and HDR.

Netflix has also said it believes a significant number of films can be remastered for HDR. So as the format takes off, we’ll likely see more and more options to stream our favourite shows and films in HDR.


So should I buy an HDR TV?

Now that there’s an official HDR standard, in the form of Ultra HD Premium, the danger of buying a rubbish TV claiming to be HDR compatible has been minimised. If you buy a Ultra HD Premium TV you’ll know you’re getting a TV capable of meeting the HDR standards set by the UHD Alliance.

It’s still worth doing some research on the product before you buy, just to ensure you’re getting the specs you need for a true HDR experience.

That said, now is a better time to invest in HDR than ever. Although 4K has been the big thing thus far, the combination of the relative ease with which HDR content can be produced (versus data-heavy 4K) and (because it’s less data intensive) distributed to consumers really seem to be exciting content producers in a way 4K struggled to do.

Put simply, content creators have more reasons to produce HDR content than 4K, so buying an HDR TV this year is a smart move. And, if you’re ready to make the move to HDR, go take a look at our best TV guide for the best options.

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