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WHAT IS HDR?


HDR stands for High Dynamic Range, and it's something that's becoming increasingly important in new consumer television sets and in the technical standard of 4K UHD images. HDR television displays images with a greater colour gamut (range and nuance) and much higher contrast. A television screen’s brightness is measured in nits, which is a unit of visible light intensity. Current HD televisions have a maximum brightness of 100 nits, while new HDR televisions have a maximum of 1000 nits. This doesn't actually represent 10x the brightness but rather the possibility for much greater contrast within the broadcast image, although HDR content does look brighter and sharper.

Since 1990, HDTV has been based around Rec709, which defines the colour values within which HD television is posted and broadcast. It represents between 7 and 9 stops of dynamic range. HDR brings with it a new standard called Rec2020 and this represents an improvement of up to 14 stops of dynamic range. Which, when you consider each stop of dynamic range represents a doubling of light intensity, is a huge leap forward. This means much greater detail can be seen within bright highlights and dark shadows. Colours and nuances within colours are also much better defined and more vivid, making the HDR image a much-improved representation of what the human eye can see.

For 4K UHD, the addition of HDR is called 'UHD Premium'.


HOW SIGNIFICANT IS IT?


SMPTE and industry trade bodies are in agreement that incorporating HDR to create UHD Premium is a true advance and significantly more impactful than the uplift from HD to 4K UHD. Their conclusions can be summarised as:

  • Broadcast images are much closer to real life images
  • The 'wow' factor is immediately noticeable for the consumer
  • That wow factor is maintained irrespective of how near or far the consumer sits from the television screen (an issue with watching 4K UHD at home)
  • The additional bandwidth uplift required (whether broadcasting HD or 4K UHD) to broadcast HDR is minimal to the point of irrelevant

Consumer televisions equipped for HDR are currently still very rare and the first generation deemed a little disappointing when compared to what can be seen on an HDR-capable Grade 1 monitor in post production. The second generation looks more promising. In time, HDR – whether HD or 4K UHD – may well become the norm, but it's going to take some time before HDR demos become commonplace in high street electronic stores.

Amazon and Netflix have again been early adopters and in both cases are commissioning HDR content in 4K UHD. If looking ahead with a valuable 4K UHD commission, it might be worth considering your workflow includes a grade for Rec709 for immediate distribution and a second ungraded master that links your edit back to your original ungraded assets. HDR is unlikely to be a flash in the pan and will change our experience of television whether in HD or 4K UHD.


HDR WORKFLOWS – WHAT’S NEW?


Acquisition

Modern digital cinematography cameras such as the Arri Alexa, Amira and Mini, the Red Dragon or Weapon, Sony F55 or F65, the Canon C300 Mk II and the Panasonic VariCam 35 all capture images with enough latitude and colour gamut for any HDR production. However, shooting RAW is strongly recommended because of the higher bit rate.

There are limited options for monitoring in HDR on-set, although the new Atomos Flame, which is a RAW recorder, player and monitor, comes complete with a 1,500-nit display. Although preferred, HDR monitoring is not essential.

Offline

You can offline in HDR on both Adobe Premiere and DaVinci Resolve, although to review in full HDR would require a very expensive Grade 1 monitor such as the Sony BVM-X300, most likely an unnecessary expense.

Grading

Most high-end colour grading systems (Baselight or DaVinci Resolve) can already grade and master in 4K UHD HDR with a significant amount of processing power. Currently the UHD Alliance only recognises the Sony BVM-X300 for HDR monitoring and HDR colour grading. So, HDR mastering will only be available from a small handful

Leica, Blackmagicdesign, Sony, ARRI, Canon, ZEISS, TLS, Panasonic

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