Fifty shades of HDR

From relatively unknown, just 5 years ago, High Dynamic Range (HDR) video is now having a major impact on most aspects of imaging. Although one of the five components of the specification for UHDTV, ITU-R Recommendation BT.2020 in 2012, it is only when it became apparent that HDR could help accelerate the slow penetration of 4K into the TV and home-cinema market, that HDR suddenly started to gain significant attention. But what exactly is HDR? Dynamic range is defined as the difference between the largest and smallest useable signal. In photography this has meant the luminance range of the scene being photographed. However, as HDR grows as a “marketing tool” this definition is becoming less “black & white”. This paper considers the different ways in which the term HDR is now being exploited; the challenges of achieving a complete efficient HDR pipeline from capture to display for a variety of applications; and, what could be done to help ensure HDR algorithms are future proof as HDR technology rapidly improves.