If you are curious about where high dynamic range stands, the differences between the BBC and NHK’s Hybrid Log-Gamma (HLG) and Dolby’s Perceptual Quantizer (PQ) HDR systems, why each exists and how the two got tucked under the same umbrella by the ITU, take out a few minutes to read “Hot Button Discussion: Inside the HDR Spec,” by Michael Goldman in the December edition of SMPTE NewsWatch.
Author Goldman interviews Tim Borer, lead engineer for Immersive and Interactive Content at the BBC’s Research and Development Division in the article. According to Borer, there are two ideas that are important to understand when considering HDR. First, broadcasters cannot know what device viewers are using to watch their programming nor the environment where it’s located. Second, manufacturers and broadcasters “should avoid thinking in terms of a single, one-size-fits-all solution” to HDR.
Perhaps the most significant difference between the two approaches is that HLG was designed to encode the signal coming directly out of the camera for HDR, whereas PQ relies on metadata added to the content in post to instruct the display device on what the image looked like on a grading monitor so that it can be reproduced for public viewing, the article says.
The former approach may be better suited for a typical TV viewing environment whereas the latter works best under controlled viewing conditions normally associated with movie theaters, the article says.
There’s a lot more to the article than these highlights, and if you are curious to learn about HDR, the SMPTE NewsWatch piece is a good place to start.