This works by assigning two different ways to decode luminance for the low and high halves of a high-dynamic range signal. The low part uses a standard gamma curve, while the higher part uses a logarithmic curve. While the HLG image may be a bit different from a non HLG HDR image, it is perceptibly HDR-looking to the user.
HLG brings the enormous benefit that it is compatible with regular TVs, so broadcasters and content-creators will not need to create two different delivery systems, which in turn saves time and money to everyone. Since HLG has support from the Association of Radio Industries and Businesses (ARIB), and is royalty-free, it has good chances of being adopted by the broadcast industry. Expect HDR to be heavily promoted as the next new thing after “4K”…