What is Hybrid Log Gamma? The future of BBC UHD TV
Want the best-ever picture for watching football and films? Hybrid Log Gamma was developed by the BBC to unlock the very best from 4K HDR. Find out more…
03 Apr 2018
The TV world is full of off-putting acronyms and jargon: 4K, OLED, HDR... and now there’s a new kid on the block: Hybrid Log Gamma. But its benefits more than justify its name.
We explain how it can rock your TV this summer…
What is Hybrid Log Gamma?
Put simply, Hybrid Log Gamma (or HLG) is a viewing format that vastly improves the picture quality of the top-of-the-range 4K HDR TVs. It's something you shouldn’t ignore if you’re on the hunt for a 4K HDR TV.
Imagine a rainforest scene, where every rain drop reflects the sunlight and sends beams shimmering, lifelike, right before your eyes. Now imagine this live without any on-demand service subscription or Blu-ray. Like the sound of that? Meet HLG.
HLG combines Standard Dynamic Range (SDR) with High Dynamic Range (HDR) images into a single video signal, making every image come alive with bright, vivid colour, no matter what TV you’ve got.
But how does it do that? With the help of its – brace yourself – Electro-Optical Transfer Function, or EOTF for short.
EOTF provides the link between recorded electrical video signal and image brightness. This information then converts digital signal data into visible light for video players. HLG uses a ‘hybrid’ EOTF that mixes two sorts of light coding, to produce overall brilliantly lifelike images and sparkling light on your TV screen.
Incredibly clever people at the BBC and Japanese broadcaster NHK worked together to develop it – testing it with a short iPlayer clip of BBC Planet Earth II.
The BBC has already announced that more 4K HDR content using Hybrid Log Gamma is expected from the BBC this summer. In fact, they’ve recently announced that some people will be able to view this summer’s football tournament in 4K HDR via BBC iPlayer.
Bringing HDR to everyone
HDR or high dynamic range is currently the most essential technology found on the best TVs. Whereas 4K increases the number of pixels making up a TV screen, HDR improves the quality of those pixels.
Watching in HDR is both realistic and immersive.
‘Water can glisten, stars can twinkle, and sunlight can be golden, all whilst maintaining detail in the shadows,’ in the words of the BBC.
HDR content comes in different formats – the most common one currently being HDR 10. But creating content that can work for broadcast TV has been a challenge.
The BBC designed Hybrid Log Gamma to bring HDR to more people by addressing the needs of TV broadcasters.
Phil Layton of BBC Research and Development explains, ‘Crucially, HLG works with existing TV technology and workflows making it ideal for broadcasters, and audiences, all over the world.’
The BBC has been experimenting with 4K HLG HDR for many months. The flagship Planet Earth II series was made available in 4K HLG HDR in a 4-minute clip on BBC iPlayer.
The footage was striking: a frog in a ‘shade of red never before seen on TV’ and raindrops in intricate detail.
It followed this up in December by making the whole Blue Planet II series available in 4K HLG HDR.
What Hi-Fi tested Blue Planet on a top of the range OLED 4K HDR TV and they were impressed:
‘Close-ups of the coral colonies of polyps fill the screen with intense (but believable) colour, and even small lightning-blue specs on a Grouper leap from its grey scales’ they wrote.
And last month the Beeb announced that this summer’s big football tournament will be shown in4K HLG HDR via BBC iPlayer.
But the coverage will be limited on a first-come, first-served basis to just ‘tens of thousands’ of people. To enjoy the ultimate picture quality, you’ll need to be among the first to click on the relevant home screen button just after streaming starts.
You’ll also benefit from having 40 Mbit/s (megabit per second) internet connection – faster than most of us have at home. That’s not to say you can’t watch it with a slower connection, you just won’t get the full 4K HDR experience.
In the mean time, have a browse of our Ultra HD televisions