High dynamic range (HDR) is a dynamic range higher than usual, synonyms are wide dynamic range, extended dynamic range, expanded dynamic range. The term is often used in discussing the dynamic range of various

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

s such as

image An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensio ...

video Video is an Electronics, electronic medium for the recording, copying, playback, broadcasting, and display of moving picture, moving image, visual Media (communication), media. Video was first developed for mechanical television systems, whi ...

s, audio or

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transm ...

. It may apply to the means of recording, processing, and reproducing such signals including

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analo ...

and digitized signals. The term is also the name of some of the technologies or techniques allowing to achieve high dynamic range images, videos, or audio.

Imaging

In this context, the term ''high dynamic range'' means there is a lot of variation in light levels within a scene or an image. The '' dynamic range'' refers to the range of

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a s ...

between the brightest area and the darkest area of that scene or image. (HDRI) refers to the set of

imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to create, preserve, or duplicate images. ...

technologies and techniques that allow to increase the dynamic range of images or videos. It covers the acquisition, creation, storage, distribution and display of images and videos. Modern movies have often been filmed with cameras featuring a higher dynamic range, and

legacy In law, a legacy is something held and transferred to someone as their inheritance, as by will and testament. Personal effects, family property, marriage property or collective property gained by will of real property. Legacy or legacies may refer ...

movies can be converted even if manual intervention would be needed for some frames (as when black-and-white films are converted to color). Also, special effects, especially those that mix real and synthetic footage, require both HDR shooting and rendering. HDR video is also needed in applications that demand high accuracy for capturing temporal aspects of changes in the scene. This is important in monitoring of some industrial processes such as welding, in predictive driver assistance systems in automotive industry, in surveillance video systems, and other applications.

Capture

photography Photography is the visual art, art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It i ...

and

videography Videography is the process of capturing moving images on electronic media (e.g., videotape, direct to disk recording, or solid state storage) and even streaming media. The term includes methods of video production and post-production. It us ...

, a technique, commonly named ''

high dynamic range High dynamic range (HDR) is a dynamic range higher than usual, synonyms are wide dynamic range, extended dynamic range, expanded dynamic range. The term is often used in discussing the dynamic range of various signals such as images, videos, ...

'' (''HDR''), allows to increase the dynamic range of captured photos and videos beyond the native capability of the camera. It consists of capturing multiple frames of the same scene but with different exposures and then combining them into one, resulting into an image with a dynamic range higher than those of individually captured frames."Compositing Multiple Pictures of the Same Scene", by Steve Mann, in IS&T's 46th Annual Conference, Cambridge, Massachusetts, May 9–14, 1993 Some of the sensors on modern phones and cameras may even combine the two images on-chip. This also allows a wider dynamic range being directly available to the user for display or processing without in-pixel compression. Some cameras designed for use in security applications can capture HDR videos by automatically providing 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.. Modern CMOS

image sensor An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of c ...

s can often capture a high dynamic range images from a single exposure. This reduces the need to use the multi-exposure HDR capture technique. High dynamic range captured images are 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.

Rendering

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).

Dynamic range compression or expansion

The technologies used to store, transmit, display and print images have limited dynamic range. When captured or created images have a higher dynamic range, they must be tone mapped in order to reduce that dynamic range.

Storage

High-dynamic-range formats for image and video files are able to store more dynamic range than traditional 8-bit gamma formats. These formats include: * Formats that are only used for storage purpose, such as: **

Raw image format A camera raw image file contains unprocessed or minimally processed data from the image sensor of either a digital camera, a motion picture film scanner, or other image scanner. Raw files are named so because they are not yet processed and the ...

s **Formats that use a

linear Linearity is the property of a mathematical relationship ('' function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear ...

transfer function In engineering, a transfer function (also known as system function or network function) of a system, sub-system, or component is a mathematical function that theoretically models the system's output for each possible input. They are widely used ...

with high bit-depth **Formats that use a

logarithmic Logarithmic can refer to: * Logarithm, a transcendental function in mathematics * Logarithmic scale, the use of the logarithmic function to describe measurements * Logarithmic spiral, * Logarithmic growth * Logarithmic distribution, a discrete pr ...

transfer function ** OpenEXR **

ACES ACeS (PT Asia Cellular Satellite) was a regional satellite telecommunications company based in Jakarta, Indonesia. It offered GSM-like satellite telephony services to Asian market. The coverage area included Indonesia, Malaysia, Thailand, Phili ...

* HDR formats that can be used for both storage and transmission to displays, such as: **

HDR10 HDR10 Media Profile, more commonly known as HDR10, is an open high-dynamic-range video (HDR) standard announced on 27 August 2015 by the Consumer Technology Association. It is the most widespread of the HDR formats. HDR10 is not backward comp ...

** HDR10+ **

Dolby Vision Dolby Vision is a set of technologies developed by Dolby Laboratories for high dynamic range (HDR) video. It covers content creation, distribution, and playback. It includes dynamic metadata that are used to adjust and optimize each frame of the ...

** HLG OpenEXR was created in 1999 by

Industrial Light & Magic Industrial Light & Magic (ILM) is an American motion picture visual effects company that was founded on May 26, 1975 by George Lucas. It is a division of the film production company Lucasfilm, which Lucas founded, and was created when he began ...

(ILM) and released in 2003 as an

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

software library In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and sub ...

. OpenEXR is used for film and

television Television, sometimes shortened to TV, is a telecommunication Media (communication), medium for transmitting moving images and sound. The term can refer to a television set, or the medium of Transmission (telecommunications), television tra ...

production.

Academy Color Encoding System The Academy Color Encoding System (ACES) is a color image encoding system created under the auspices of the Academy of Motion Picture Arts and Sciences. ACES allows for a fully encompassing color accurate workflow, with "seamless interchange of ...

(ACES) was created by the

Academy of Motion Picture Arts and Sciences The Academy of Motion Picture Arts and Sciences (AMPAS, often pronounced ; also known as simply the Academy or the Motion Picture Academy) is a professional honorary organization with the stated goal of advancing the arts and sciences of motion ...

and released in December 2014. ACES is a complete color and file management system that works with almost any professional workflow and it supports both HDR and wide color gamut. More information can be found a
https://www.ACESCentral.com
(WCG).

Transmission to displays

High dynamic range High dynamic range (HDR) is a dynamic range higher than usual, synonyms are wide dynamic range, extended dynamic range, expanded dynamic range. The term is often used in discussing the dynamic range of various signals such as images, videos, ...

(HDR) is also the common name of a technology allowing to transmit high dynamic range videos and images to compatible displays. That technology also improves other aspects of transmitted images, such as color gamut. In this context, * HDR displays refers to displays compatible with that technology. * HDR formats refers to formats such as

, HDR10+,

and HLG. * HDR video refers to a video encoded in an HDR format. Thoses HDR video have a greater bit depth, luminance and color volume than

standard dynamic range Standard-dynamic-range (SDR) video is a video technology which represents light intensity based on the brightness, contrast and color characteristics and limitations of a cathode ray tube (CRT) display. SDR video is able to represent a video or p ...

(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 The contrast ratio (CR) is a property of a display system, defined as the ratio of the luminance of the brightest shade (white) to that of the darkest shade (black) that the system is capable of producing. A high contrast ratio is a desired aspe ...

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 A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but in ...

and

OLED An organic light-emitting diode (OLED or organic LED), also known as organic electroluminescent (organic EL) diode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light ...

. Some options to use HDR

s that better match the human

visual system The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight ...

other than a conventional gamma curve include the HLG and

perceptual quantizer The perceptual quantizer (PQ), published by SMPTE as SMPTE ST 2084, is a transfer function that allows for HDR display by replacing the gamma curve used in SDR. It is capable of representing luminance level up to 10000 cd/m2 (nits) and down to ...

(PQ). HLG and PQ require a bit depth of 10-bits per sample.

Display

The dynamic range of a display refers to range of

the display can reproduce, from the black level to its peak brightness. The contrast of a display refers to the

ratio In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...

between the luminance of the brightest white and the darkest black that a monitor can produce. Multiple technologies allowed to increase the dynamic range of displays. In May 2003, BrightSide Technologies demonstrated the first HDR display at the Display Week Symposium of the

Society for Information Display The Society for Information Display (SID) is an industry organization for displays, generally electronic displays such as televisions and computer monitors. SID was founded in September 1962. Its main activities are publishing technical journals an ...

. The display used an array of individually-controlled LEDs behind a conventional LCD panel in a configuration known as " local dimming" today. BrightSide later introduced a variety of related display and video technologies enabling visualization of HDR content. In April 2007, BrightSide Technologies was acquired by

Dolby Laboratories Dolby Laboratories, Inc. (often shortened to Dolby Labs and known simply as Dolby) is an American company specializing in audio noise reduction, audio encoding/compression, spatial audio, and HDR imaging. Dolby licenses its technologies to ...

displays have high contrast. MiniLED improves contrast.

Audio

In Audio, the term ''high dynamic range'' means there is a lot of variation in the levels of the sound. Here, the '' dynamic range'' refers to the range between the highest volume and lowest volume of the sound. 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 EA Digital Illusions CE AB (trade name: DICE) is a Swedish video game developer based in Stockholm. The company was founded in 1992 and has been a subsidiary of Electronic Arts since 2006. Its releases include the ''Battlefield'', ''Mirror's Edg ...

Frostbite Engine to allow relatively louder sounds to drown out softer sounds.

Dynamic range compression Dynamic range compression (DRC) or simply compression is an audio signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds, thus reducing or ''compressing'' an audio signal's dynamic range. Compression is ...

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 Spurious-free dynamic range (SFDR) is the strength ratio of the fundamental signal to the strongest spurious signal in the output. It is also defined as a measure used to specify analog-to-digital and digital-to-analog converters (ADCs and DACs, re ...

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 Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in analog hardware (e.g. mixers, filters, amplifiers, modulators/ demodulators, detectors, etc.) are instead implemented b ...

design.

Instrumentation

In many fields, instruments need to have a very high dynamic range. For example, in

seismology Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

, 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".

References

External links

*{{cite web , title=High Dynamic Range (HDR) on Intel Graphics , publisher=Intel Corporation , url=https://www.intel.com/content/dam/support/us/en/documents/graphics/HDR_Intel_Graphics_TechWhitePaper.pdf , date= November 2017 Broad-concept articles Display technology Electrical engineering Film and video technology Television technology