High dynamic range
High dynamic range (HDR) is a dynamic range higher than what is considered to be standard dynamic range. The term is often used in discussing display devices, photography, 3D rendering, and sound recording including digital imaging and digital audio production. The term may apply to an analog or digitized signal, or to the means of recording, processing, and reproducing such signals.[1]
Visual
High-dynamic-range imaging (HDRI) is the compositing and tone-mapping of images to extend the dynamic range beyond the native capability of the capturing device.[2][3]
High-dynamic-range video (HDR video) refers to a video signal with greater bit depth, luminance and color volume than standard dynamic range (SDR) video which uses a conventional gamma curve.[4]
High-dynamic-range rendering (HDRR) is the real-time rendering and display of virtual environments using a dynamic range of 65,535:1 or higher (used in computer, gaming, and entertainment technology).[5]
On January 4, 2016, the Ultra HD Alliance announced their certification requirements for a HDR display.[6][7] The HDR display must have either a peak brightness of over 1000 cd/m2 and a black level less than 0.05 cd/m2 (a contrast ratio of at least 20,000:1) or a peak brightness of over 540 cd/m2 and a black level less than 0.0005 cd/m2 (a contrast ratio of at least 1,080,000:1).[6][7] The two options allow for different types of HDR displays such as LCD and OLED.[7]
Some options to use HDR transfer functions that better match the human visual system other than a conventional gamma curve include the Hybrid Log-Gamma (HLG) and Perceptual Quantizer (PQ).[4][8][9] HLG and PQ require a bit depth of 10-bits per sample.[4][8]
HDR is available in Home Cinema with Kaleidescape's media servers at 60 frames per second in individual home cinemas.[10]
Audio
XDR (audio) is used to provide higher-quality audio when using microphone sound systems or recording onto cassette tapes.
HDR Audio is a dynamic mixing technique used in EA Digital Illusions CE Frostbite Engine to allow relatively louder sounds to drown out softer sounds.[11]
Dynamic range compression is a set of techniques used in audio recording and communication to put high-dynamic-range material through channels or media of lower dynamic range. Optionally, dynamic range expansion is used to restore the original high dynamic range on playback.
Radio
In radio, high dynamic range is important especially when there are potentially interfering signals. Measures such as spurious-free dynamic range are used to quantify the dynamic range of various system components such as frequency synthesizers. HDR concepts are important in both conventional and software-defined radio design.
Instrumentation
In many fields, instruments need to have a very high dynamic range. For example, in seismology, HDR accelerometers are needed, as in the ICEARRAY instruments.
Realtime HDR vision
In the 1970s and 1980s, Steve Mann invented the Generation-1 and Generation-2 "Digital Eye Glass", as a vision aid to help people see better, with some versions being built into welding helmets for HDR vision [12] [13] [14] [15] See also, IEEE Technology and Society Magazine 31(3)[16] and the supplemental material entitled "GlassEyes".
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