08 Mar 2017

HDR: de-confusing the standards

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Dolby rendering of the effects of HDR Dolby rendering of the effects of HDR Dolby

Index

Elephant in the room

When it comes to displays, it is therefore very important to be aware of what standards it displays. This is important because the screen that you choose really should be based upon what you view, and importantly, where.

We are all used to having the ability to adjust our television brightness to account of the viewing conditions. In bright sunshine you may well want to increase the brightness of your set. Unfortunately some standards of HDR come with a fairly large limitation. Both HDR10 and Dolby Vision are shown on ST-2084 compliant monitors. These are the two best known HDR standards and are seen as the current pinnacle of quality viewing. But what you might not know about them is that whilst both are designed to adapt to the different capabilities of the monitor or television being viewed, they are also designed to have the maximum available dynamic range on that display available on tap at all times.

This means that if you want to adjust the brightness of the monitor to account for ambient light conditions, you’ll be out of luck. So viewed in a bright sunny room some scenes may appear very dark. Whilst in dark viewing environments, they could appear overly bright and cause eye strain. Furthermore, while both standards are designed to adapt to different monitors dynamic range capabilities, there is no set standard way to achieve this remapping of the transfer curve. So from monitor to monitor, the viewing results could be very different indeed.

As a result, if you are looking to view Dolby Vision or HDR10 material, you generally need to have a good amount of control over your viewing environment and the ambient light.

This isn’t the case with displays that cater for HLG (Hybrid Log Gamma). HLG was developed by the BBC and NHK as an open standard. Unlike HDR10 and Dolby Vision, HLG capable displays can have their system specific gamma adjusted based upon ambient conditions, and so the viewing environment is not so critical.

Complexity unraveled. Sort of...

One of the complexities of understanding HDR in terms that mortals can understand, is that many of the terms used are not really that relevant to the vast majority of monitor and television customers. The various specifications and standards have a lot of crossover, too. In addition there can be a lot of complexity with regards to the display environment, and the effect HDR will have on your eyes. This latter point will be of great importance to the creatives who shoot and grade their productions. But for the average consumer, what is important is that the display that you buy does what you need it to do.

HLG is already supported by online services such as YouTube, and it is also already supported by HDMI 2.0b, the HEVC encoding standard, and VP9. Both Dolby Vision and HDR10 are being supported by most of the big television manufacturers. LG for example has announced that all of its HDR capable televisions will be supporting Dolby Vision, HDR10, and HLG. In fact any HDR capable television that has the capability of showing internet based viewing such as YouTube, as the majority of televisions do these days, will likely have HLG compatibility going forward.

It would seem, then, that we may not have the format wars mess that has plagued new technology in the past. Instead monitor and television manufacturers are tending to prefer to hedge their bets by not placing all their eggs in one basket. But even if your display can show all standards of content, the caveats of viewing environment restrictions still apply to the Dolby Vision and HDR10 based output.

Therefore, much more important than any of the various standards is going to be where you are viewing the display. More than anything else, this will either ruin and render your HDR experience pointless, or it will give you the best viewing experience you have had.

If I was to hedge my bets on a personal level, I feel that HLG has good legs, simply because it is more accessible to a wider variety of content makers, offers adaptability to different displays, and is backwards compatible with SDR systems. In other words it offers a convenience that is not provided elsewhere. But don’t ask me to place money on it! But I hope that I have simplified things enough for most people to understand.

I realise that there are many different points to make about the different specifications and standards, so I will not have satisfied the hardened technical nuts. But as anyone who has attempted to read through an HDR white paper knows, such topics can run for many pages, with much of the information irrelevant for the majority of television and monitor customers. Right, I’m off to take some paracetamol!




Simon Wyndham

Simon Wyndham is Deputy Editor of RedShark News, a professional cameraman and video producer of over 15 years. With a background in indy feature making, when he isn't producing bread and butter corporate videos he can be found hucking the gnar on rivers whitewater kayaking and adventure sports filming.

Website: www.5ep.co.uk

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