High dynamic range

High dynamic range (HDR) is a dynamic range higher than usual. 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.
Imaging.
High dynamic range imaging (HDRI) refers to the acquisition, creation, storage, distribution or display of images and videos that have a higher dynamic range than traditional images and videos. This can be done with the HDR photography technique, with the use of cameras that natively have a high dynamic range or with computers (for example with the use of HDR rendering). The resulting image can be saved in an traditional image and video format or in an high dynamic range format. It can also be used for traditional SDR displays or for HDR displays.
Capture and creation.
Photography technique.
In photography and videography, High Dynamic Range (HDR) is a technique used to increase the dynamic range of captured photos and videos. It consist of capturing multiple frames of the same scene but with different exposures and then combining them into one resulting into a dynamic range higher than those of individualy captured frames. 
It includes the compositing and tone mapping of images to extend the dynamic range beyond the native capability of the capturing device.
Sensors.
Modern CMOS image sensors can often capture a high dynamic range from a single exposure. The wide dynamic range of the captured image is non-linearly compressed into a smaller dynamic range electronic representation. However, with proper processing, the information from a single exposure can be used to create an HDR image.
Such HDR imaging is used in extreme dynamic range applications like welding or automotive work. In security cameras the term used instead of HDR is "wide dynamic range". Because of the nonlinearity of some sensors image artifacts can be common. Some other cameras designed for use in security applications can automatically provide two or more images for each frame, with changing exposure . For example, a sensor for 30fps video will give out 60fps with the odd frames at a short exposure time and the even frames at a longer exposure time. Some of the sensors on modern phones and cameras may even combine the two images on-chip so that a wider dynamic range without in-pixel compression is directly available to the user for display or processing.
Rendering.
High Dynamic Range Rendering (HDRR or HDR rendering) is a way of rendering computer generated images with a high dynamic range.
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).
Storage.
The term high dynamic range format designates image and video file formats that are able to store more dynamic range than traditional 8-bit gamma formats.
This includes:
Distribution and display.
High Dynamic Range displays (HDR displays) are displays compatible with a list one HDR formats such as HDR10, HDR10+, Dolby Vision and HLG.
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.
On January 4, 2016, the Ultra HD Alliance announced their certification requirements for a HDR display. 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). The two options allow for different types of HDR displays such as LCD and OLED.
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). HLG and PQ require a bit depth of 10-bits per sample.
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.
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
See also, IEEE Technology and Society Magazine 31(3) and the supplemental material entitled "GlassEyes".