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In photography 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 use ...
, multi-exposure HDR capture is a technique that creates extended or high dynamic range (HDR) images by taking and combining multiple exposures of the same subject matter at different exposure levels. Combining multiple images in this way results in an image with a greater dynamic range than what would be possible by taking one single image. The technique can also be used to capture video by taking and combining multiple exposures for each frame of the video. The term "HDR" is used frequently to refer to the process of creating HDR images from multiple exposures. Many smartphones have an automated HDR feature that relies on
computational imaging Computational imaging is the process of indirectly forming images from measurements using algorithms that rely on a significant amount of computing. In contrast to traditional imaging, computational imaging systems involve a tight integration of th ...
techniques to capture and combine multiple exposures. A single image captured by a camera provides a finite range of luminosity inherent to the medium, whether it is a digital sensor or film. Outside this range, tonal information is lost and no features are visible; tones that exceed the range are "burned out" and appear pure white in the brighter areas, while tones that fall below the range are "crushed" and appear pure black in the darker areas. The ratio between the maximum and the minimum tonal values that can be captured in a single image is known as the
dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of signals, like sound and light. It is measured either as a ratio or as a base- ...
. In photography, dynamic range is measured in
exposure value In photography, exposure value (EV) is a number that represents a combination of a camera's shutter speed and f-number, such that all combinations that yield the same exposure have the same EV (for any fixed scene luminance). Exposure value is a ...
(EV) differences, also known as ''stops''. This technique can be applied to produce images that preserve local contrast for a natural rendering, or exaggerate local contrast for artistic effect. HDR is useful for recording many real-world scenes containing very bright, direct sunlight to extreme shade, or very faint nebulae. Due to the limitations of printing and
display contrast Contrast in visual perception is a felt difference in appearance of two or more parts of a field seen simultaneously or successively (hence: brightness contrast, lightness contrast, color contrast, simultaneous contrast, successive contrast, etc.). ...
, the extended dynamic range of HDR images must be compressed to the range that can be displayed. The method of rendering a high dynamic range image to a standard monitor or printing device is called tone mapping. This method reduces the overall contrast of an HDR image to facilitate display on devices or printouts with lower dynamic range.


Benefits

One aim of HDR is to present a similar range of luminance to that experienced through 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 (the ...
. The human eye, through non-linear response,
adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...
of the
iris Iris most often refers to: *Iris (anatomy), part of the eye *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (color), an ambiguous color term Iris or IRIS may also refer to: Arts and media Fictional ent ...
, and other methods, adjusts constantly to a broad range of luminance present in the environment. The brain continuously interprets this information so that a viewer can see in a wide range of light conditions. Most cameras are limited to a much narrower range of exposure values within a single image, due to the dynamic range of the capturing medium. With a limited dynamic range, tonal differences can be captured only within a certain range of brightness. Outside of this range, no features are visible: when the tone being captured exceeds the range in bright areas, these tones appear as pure white, and when the tone being captured does not meet the minimum threshold, these tones appear as pure black. Images captured with non-HDR cameras that have a limited exposure range, referred to as low dynamic range (LDR), can result in the loss of detail in highlights or
shadows A shadow is a dark area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, ...
. Modern
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...
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 cu ...
s have improved dynamic range and can often capture a wider range of tones in a single exposure reducing the need to perform multi-exposure HDR. Color film negatives and slides consist of multiple film layers that respond to light differently. Original film (especially negatives versus transparencies or slides) feature a very high dynamic range (in the order of 8 for negatives and 4 to 4.5 for slides). Multi-exposure HDR is used in photography and also in extreme dynamic range applications like welding or automotive work. In security cameras the term used instead of HDR is "wide dynamic range".


Limitations

A fast-moving subject (or unsteady camera) will result in a "ghost" effect or a staggered-blur strobe effect, as a result of the merged images not being identical, but each capturing the moving subject at a different moment in time, with its position changed. Sudden changes in the lighting conditions (strobed LED light) can also interfere with the desired results, by producing one or more HDR layers that do have the luminosity expected by an automated HDR system, though one might still be able to produce a reasonable HDR image manually in software by rearranging the image layers to merge in order of their actual luminosity. Because of the nonlinearity of some sensors image artifacts can be common. Camera characteristics such as gamma curves, sensor resolution, noise, photometric calibration and
color calibration The aim of color calibration is to measure and/or adjust the color response of a device (input or output) to a known state. In International Color Consortium (ICC) terms, this is the basis for an additional color characterization of the device ...
affect resulting high-dynamic-range images.


Process

High-dynamic-range photographs are generally composited from multiple standard dynamic range images, often captured using exposure bracketing. Afterwards, photo manipulation software merges the input files into a single HDR image, which is then also tone mapped in accordance with the limitations of the planned output or display.


Capturing multiple images (exposure bracketing)

Any camera that allows manual exposure control can perform multi-exposure HDR image capture, although one equipped with automatic exposure bracketing (AEB) facilitates the process. Some cameras have an AEB feature that spans a far greater dynamic range than others, from ±0.6 at the low end to ±18 EV in top professional cameras, Images from film cameras generally are less suitable as the captured images require a prerequisite step of scanning and digitization so that they can later be processed using software HDR methods. The exposure value (EV) refers to the amount of light applied to the active element, whether film or digital sensor such as a CCD. An increase of one stop represents a doubling of the amount of light captured. Conversely, a decrease of one stop represents a halving of the amount of light. Therefore, revealing detail in the darkest of shadows requires an increased EV, while preserving detail in very bright situations requires very low EVs. EV is controlled using one of two photographic controls: varying either the size of the
aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opti ...
or the exposure time. A set of images with multiple EVs intended for HDR processing should be captured only by altering the exposure time; altering the aperture size also would affect the
depth of field The depth of field (DOF) is the distance between the nearest and the furthest objects that are in acceptably sharp focus in an image captured with a camera. Factors affecting depth of field For cameras that can only focus on one object dis ...
and so the resultant multiple images would be quite different, preventing their final combination into a single HDR image. Multi-exposure HDR photography generally is limited to still scenes because any movement between successive images will impede or prevent success in combining them afterward. Also, because the photographer must capture three or more images to obtain the desired luminance range, taking such a full set of images takes extra time. Photographers have developed calculation methods and techniques to partially overcome these problems, but the use of a sturdy tripod is advised to minimize framing differences between exposures.


Merging the images into an HDR image

Tonal information and details from shadow areas can be recovered from images that are deliberately overexposed (i.e., with positive EV compared to the correct scene exposure), while similar tonal information from highlight areas can be recovered from images that are deliberately underexposed (negative EV). The process of selecting and extracting shadow and highlight information from these over/underexposed images and then combining them with image(s) that are exposed correctly for the overall scene is known as
exposure fusion In image processing, computer graphics, and photography, exposure fusion is a technique for blending multiple exposures of the same scene (bracketing) into a single image. As in high dynamic range imaging In photography and videography, multi ...
. Exposure fusion can be performed manually, relying on the HDR operator's judgment, experience, and training, but usually, fusion is performed automatically by software.


Storing

Information stored in high-dynamic-range images typically corresponds to the physical values of luminance or radiance that can be observed in the real world. This is different from traditional
digital images A digital image is an image composed of picture elements, also known as ''pixels'', each with ''finite'', '' discrete quantities'' of numeric representation for its intensity or gray level that is an output from its two-dimensional functions f ...
, which represent colors as they should appear on a monitor or a paper print. Therefore, HDR image formats are often called ''scene-referred'', in contrast to traditional digital images, which are ''device-referred'' or ''output-referred''. Furthermore, traditional images are usually encoded for 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 (the ...
(maximizing the visual information stored in the fixed number of bits), which is usually called ''gamma encoding'' or '' gamma correction''. The values stored for HDR images are often gamma compressed using mathematical functions such as power laws logarithms, or
floating point In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be r ...
linear values, since
fixed-point Fixed point may refer to: * Fixed point (mathematics), a value that does not change under a given transformation * Fixed-point arithmetic, a manner of doing arithmetic on computers * Fixed point, a benchmark (surveying) The term benchmark, be ...
linear encodings are increasingly inefficient over higher dynamic ranges. HDR images often do not use fixed ranges per color channel, other than traditional images, to represent many more colors over a much wider dynamic range (multiple channels). For that purpose, they do not use integer values to represent the single color channels (e.g., 0–255 in an 8 bit per pixel interval for red, green and blue) but instead use a floating point representation. Common values are 16-bit (
half precision In computing, half precision (sometimes called FP16) is a binary floating-point computer number format that occupies 16 bits (two bytes in modern computers) in computer memory. It is intended for storage of floating-point values in applications wh ...
) or 32-bit
floating-point In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be r ...
numbers to represent HDR pixels. However, when the appropriate transfer function is used, HDR pixels for some applications can be represented with a
color depth Color depth or colour depth (see spelling differences), also known as bit depth, is either the number of bits used to indicate the color of a single pixel, or the number of bits used for each color component of a single pixel. When referring t ...
that has as few as 10 to 12 bits ( to values) for luminance and 8 bits ( values) for
chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying luma signal (or Y' for short). Chrominance is usually represen ...
without introducing any visible quantization artifacts.


Tone mapping

Tone mapping reduces the dynamic range, or contrast ratio, of an entire image while retaining localized contrast. Although it is a distinct operation, tone mapping is often applied to HDR files by the same software package. Tone mapping is often needed because the dynamic range that can be displayed is often lower than the dynamic range of the captured or processed image. HDR displays can receive a higher dynamic range signal than SDR displays, reducing the need for tone mapping.


Types of HDR

HDR can be done via several methods: * DOL: Digital overlap * BME: Binned multiplexed exposure * SME: Spatially multiplexed exposure * QBC: Quad Bayer Coding


Examples

This is an example of four standard dynamic range images that are combined to produce three resulting tone mapped images: Image:StLouisArchMultExpEV-4.72.JPG, –4 stops Image:StLouisArchMultExpEV-1.82.JPG, –2 stops Image:StLouisArchMultExpEV+1.51.JPG, +2 stops Image:StLouisArchMultExpEV+4.09.JPG, +4 stops File:StLouisArchMultExpCDR.jpg, Simple contrast reduction File:StLouisArchMultExpToneMapped.jpg, Local tone mapping File:StLouisArchMultExpEV SNS-HDR.jpg, alt=Natural tone mapping, Natural tone mapping This is an example of a scene with a very wide dynamic range: Image:HDRI Sample Scene Window - 01.jpg, –6 stops Image:HDRI Sample Scene Window - 02.jpg, –5 stops Image:HDRI Sample Scene Window - 03.jpg, –4 stops Image:HDRI Sample Scene Window - 04.jpg, –3 stops Image:HDRI Sample Scene Window - 05.jpg, –2 stops Image:HDRI Sample Scene Window - 06.jpg, –1 stops Image:HDRI Sample Scene Window - 07.jpg, 0 stops Image:HDRI Sample Scene Window - 08.jpg, +1 stops Image:HDRI Sample Scene Window - 09.jpg, +2 stops Image:HDRI Sample Scene Window - 10.jpg, +3 stops Image:HDRI Sample Scene Window - 11.jpg, +4 stops Image:HDRI Sample Scene Window - 12.jpg, +5 stops Image:HDRI Sample Scene Window.jpg, Natural tone mapping


Devices


Post-capture software

Several software applications are available on the PC, Mac, and Linux platforms for producing HDR files and tone mapped images. Notable titles include: *
Adobe Photoshop Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Microsoft Windows, Windows and macOS. It was originally created in 1988 by Thomas Knoll, Thomas and John Knoll. Since then, the software has become the indu ...
*
Affinity Photo Affinity Photo is a raster graphics editor developed by Serif Ltd. for iOS, macOS, and Windows, alongside Affinity Designer and Affinity Publisher. Development of Affinity Photo started in 2009 as a raster graphics editor for macOS. Its first v ...
* Aurora HDR * Dynamic Photo HDR * EasyHDR * GIMP * HDR PhotoStudio *
Luminance HDR Luminance HDR, formerly Qtpfsgui, is graphics software used for the creation and manipulation of high-dynamic-range images. Released under the terms of the GPL, it is available for Linux, Windows and Mac OS X (Intel only). Luminance HDR support ...
*
Nik Collection Nik Software was a software development company established in 1995 and based in San Diego, California. The company developed multiple image editing plug-ins and tools (for digital image processing applications, such as Adobe Photoshop) and Snap ...
HDR Efex Pro *
Oloneo PhotoEngine Oloneo PhotoEngine is a popular digital image editing software application developed by Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 10 ...
* Photomatix Pro * PTGui * SNS-HDR


Photography

As the popularity of this imaging method grows, several camera manufacturers are now offering built-in multi-exposure HDR features. For example, the
Pentax K-7 The Pentax K-7 is a 14.6-megapixel digital single-lens reflex camera, announced on 20 May 2009. This is the first new flagship model released by Pentax since its merger with Hoya Corporation on 31 March 2008. It was discontinued late in 2010 in f ...
DSLR has an HDR mode that take 3 or 5 shots and outputs (only) a tone mapped HDR image in a JPEG file. The
Canon PowerShot G12 The Canon PowerShot G is a series of digital cameras introduced by Canon in its PowerShot line in 2000. The G series cameras are Canon's flagship compact models aimed at photography enthusiasts desiring more flexibility than a point-and-shoot wi ...
,
Canon PowerShot S95 The Canon PowerShot S95 is a high-end 10.0-megapixel compact digital camera announced and released in 2010. It was designed as the successor to the Canon PowerShot S90 in the S series of the Canon PowerShot line of cameras. This model is conside ...
, and
Canon PowerShot S100 The Canon PowerShot S100 is a high-end 12.1-megapixel compact digital camera announced and released in 2011. It was designed as the successor to the Canon PowerShot S95 in the S series of the Canon PowerShot line of cameras. The S100 is a simila ...
offer similar features in a smaller format. Nikon's approach is called 'Active D-Lighting' which applies exposure compensation and tone mapping to the image as it comes from the sensor, with the emphasis being on creating a realistic effect. Some smartphones provide HDR modes for their cameras, and most
mobile platform A mobile operating system is an operating system for mobile phones, tablets, smartwatches, smartglasses, or other non-laptop personal mobile computing devices. While computers such as typical laptops are "mobile", the operating systems used on ...
s have apps that provide multi-exposure HDR picture taking. Google released a HDR+ mode for the Nexus 5 and Nexus 6 smartphones in 2014, which automatically captures a series of images and combines them into a single still image, as detailed by
Marc Levoy Marc Levoy is a computer graphics researcher and Professor Emeritus of Computer Science and Electrical Engineering at Stanford University, a vice president and Fellow at Adobe Inc., and (until 2020) a Distinguished Engineer at Google. He is noted ...
. Unlike traditional HDR, Levoy's implementation of HDR+ used multiple images at a short shutter speed; the resulting set of underexposed images were aligned and averaged by pixel, improving dynamic range and reducing noise. By selecting the sharpest image as the baseline for alignment, the effect of camera shake is also reduced. 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.


Videography

Although not as established as for still photography capture, it is also possible to capture and combine multiple images for each frame of a video in order to increase the dynamic range captured by the camera. This can be done via multiple methods: * Creating a
time-lapse Time-lapse photography is a technique in which the frequency at which film frames are captured (the frame rate) is much lower than the frequency used to view the sequence. When played at normal speed, time appears to be moving faster and thus ...
of individually images created via the multi-exposure HDR technique. * Taking consecutively two differently exposed images by cutting the frame rate in half. * Taking simultaneously two differently exposed images by cutting the resolution in half. * Taking simultaneously two differently exposed images with full resolution and frame rate via a sensor with dual gain architecture. For example:
Arri Alexa The Arri Alexa (stylised as ΛLEXΛ) is a digital motion picture camera system developed by Arri. First introduced in April 2010, the camera was Arri's first major transition into digital cinematography after previous efforts such as the Arri ...
's sensor, Samsung sensors with Smart-ISO Pro. Some 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. In 2020, Qualcomm announced Snapdragon 888, a mobile SoC able to do computational multi-exposure HDR video capture in 4K and also to record it in a format compatible with HDR displays. In 2021, the Xiaomi Mi 11 Ultra smartphone is able to do computational multi-exposure HDR for video capture.


Surveillance cameras

In recent years, even cheap models have been supplied with HDR capture, usually described as wide dynamic range (WDR) function, such as CarCam Tiny, Prestige DVR-390, and DVR-478.


History


Mid 19th century

The idea of using several exposures to adequately reproduce a too-extreme range of luminance was pioneered as early as the 1850s by
Gustave Le Gray Jean-Baptiste Gustave Le Gray (; 30 August 1820 – 30 July 1884)Le Corre, Florence "Translated from the catalogue ''Une visite au camp de Châlons sous le Second Empire: photographies de Messieurs Le Gray, Prévot...'', Paris: musée de l'Armée, ...
to render seascapes showing both the sky and the sea. Such rendering was impossible at the time using standard methods, as the luminosity range was too extreme. Le Gray used one negative for the sky, and another one with a longer exposure for the sea, and combined the two into one picture in positive.


Mid 20th century

Manual tone mapping was accomplished by
dodging and burning Dodging and burning are terms used in photography for a technique used during the printing process to manipulate the exposure of select areas on a photographic print, deviating from the rest of the image's exposure. In a darkroom print from a fil ...
 – selectively increasing or decreasing the exposure of regions of the photograph to yield better tonality reproduction. This was effective because the dynamic range of the negative is significantly higher than would be available on the finished positive paper print when that is exposed via the negative in a uniform manner. An excellent example is the photograph ''Schweitzer at the Lamp'' by
W. Eugene Smith William Eugene Smith (December 30, 1918 – October 15, 1978) was an American photojournalist.Peacock, Scot. "W(illiam) Eugene Smith." ''Contemporary Authors Online'', Gale, 2003. ''Biography In Context'' He has been described as "perhaps the sin ...
, from his 1954
photo essay A photographic essay or photo-essay for short is a form of visual storytelling, a way to present a narrative through a series of images. A photo essay delivers a story using a series of photographs and brings the viewer along a narrative journey. E ...
''A Man of Mercy'' on
Albert Schweitzer Ludwig Philipp Albert Schweitzer (; 14 January 1875 – 4 September 1965) was an Alsatian-German/French polymath. He was a theologian, organist, musicologist, writer, humanitarian, philosopher, and physician. A Lutheran minister, Schwei ...
and his humanitarian work in French Equatorial Africa. The image took five days to reproduce the tonal range of the scene, which ranges from a bright lamp (relative to the scene) to a dark shadow.
Ansel Adams Ansel Easton Adams (February 20, 1902 – April 22, 1984) was an American landscape photographer and environmentalist known for his black-and-white images of the American West. He helped found Group f/64, an association of photographers advoc ...
elevated dodging and burning to an art form. Many of his famous prints were manipulated in the darkroom with these two methods. Adams wrote a comprehensive book on producing prints called ''The Print'', which prominently features dodging and burning, in the context of his
Zone System The Zone System is a photographic technique for determining optimal film exposure and development, formulated by Ansel Adams and Fred Archer. Adams described the Zone System as " ..not an invention of mine; it is a codification of the principle ...
. With the advent of color photography, tone mapping in the darkroom was no longer possible due to the specific timing needed during the developing process of color film. Photographers looked to film manufacturers to design new film stocks with improved response, or continued to shoot in black and white to use tone mapping methods. Color film capable of directly recording high-dynamic-range images was developed by Charles Wyckoff and
EG&G EG&G, formally known as Edgerton, Germeshausen, and Grier, Inc., was a United States national defense contractor and provider of management and technical services. The company was involved in contracting services to the United States government ...
"in the course of a contract with the Department of the Air Force". This XR film had three emulsion layers, an upper layer having an
ASA ASA as an abbreviation or initialism may refer to: Biology and medicine * Accessible surface area of a biomolecule, accessible to a solvent * Acetylsalicylic acid, aspirin * Advanced surface ablation, refractive eye surgery * Anterior spinal a ...
speed rating of 400, a middle layer with an intermediate rating, and a lower layer with an ASA rating of 0.004. The film was processed in a manner similar to color films, and each layer produced a different color. The dynamic range of this extended range film has been estimated as 1:108. It has been used to photograph nuclear explosions, for astronomical photography, for spectrographic research, and for medical imaging. Wyckoff's detailed pictures of nuclear explosions appeared on the cover of '' Life'' magazine in the mid-1950s.


Late 20th century

Georges Cornuéjols and licensees of his patents (Brdi, Hymatom) introduced the principle of HDR video image, in 1986, by interposing a matricial LCD screen in front of the camera's image sensor, increasing the sensors dynamic by five stops. The concept of neighborhood tone mapping was applied to video cameras in 1988 by a group from the Technion in Israel, led by Oliver Hilsenrath and Yehoshua Y. Zeevi. Technion researchers filed for a patent on this concept in 1991, and several related patents in 1992 and 1993. In February and April 1990, Georges Cornuéjols introduced the first real-time HDR camera that combined two images captured successively by a sensor or simultaneously by two sensors of the camera. This process is known as
bracketing In photography, bracketing is the general technique of taking several shots of the same subject using different camera settings. Bracketing is useful and often recommended in situations that make it difficult to obtain a satisfactory image with ...
used for a video stream. In 1991, the first commercial video camera was introduced that performed real-time capturing of multiple images with different exposures, and producing an HDR video image, by Hymatom, licensee of Georges Cornuéjols. Also in 1991, Georges Cornuéjols introduced the HDR+ image principle by non-linear accumulation of images to increase the sensitivity of the camera: for low-light environments, several successive images are accumulated, thus increasing the
signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in de ...
. In 1993, another commercial medical camera producing an HDR video image, by the Technion. Modern HDR imaging uses a completely different approach, based on making a high-dynamic-range luminance or light map using only global image operations (across the entire image), and then tone mapping the result. Global HDR was first introduced in 1993 resulting in a mathematical theory of differently exposed pictures of the same subject matter that was published in 1995 by Steve Mann and
Rosalind Picard Rosalind Wright Picard (born May 17, 1962) is an American scholar and inventor who is Professor of Media Arts and Sciences at MIT, founder and director of the Affective Computing Research Group at the MIT Media Lab, and co-founder of the startups ...
. On October 28, 1998, Ben Sarao created one of the first nighttime HDR+G (high dynamic range + graphic) image of
STS-95 STS-95 was a Space Shuttle mission launched from Kennedy Space Center, Florida on 29 October 1998, using the orbiter ''Discovery''. It was the 25th flight of ''Discovery'' and the 92nd mission flown since the start of the Space Shuttle program ...
on the launch pad at NASA's Kennedy Space Center. It consisted of four film images of the space shuttle at night that were digitally composited with additional digital graphic elements. The image was first exhibited at NASA Headquarters Great Hall, Washington DC, in 1999 and then published in ''Hasselblad Forum''. The advent of consumer digital cameras produced a new demand for HDR imaging to improve the light response of digital camera sensors, which had a much smaller dynamic range than film. Steve Mann developed and patented the global-HDR method for producing digital images having extended dynamic range at the MIT Media Lab. Mann's method involved a two-step procedure: First, generate one floating point image array by global-only image operations (operations that affect all pixels identically, without regard to their local neighborhoods). Second, convert this image array, using local neighborhood processing (tone-remapping, etc.), into an HDR image. The image array generated by the first step of Mann's process is called a ''lightspace image'', ''lightspace picture'', or ''radiance map''. Another benefit of global-HDR imaging is that it provides access to the intermediate light or radiance map, which has been used for
computer vision Computer vision is an interdisciplinary scientific field that deals with how computers can gain high-level understanding from digital images or videos. From the perspective of engineering, it seeks to understand and automate tasks that the human ...
, and other
image processing 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-dimension ...
operations.


21st century

In February 2001, the Dynamic Ranger technique was demonstrated, using multiple photos with different exposure levels to accomplish high dynamic range similar to the naked eye. In the early 2000s, several scholarly research efforts used consumer-grade sensors and cameras. A few companies such as
RED Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...
and
Arri The Arri Group () is a German manufacturer of motion picture film equipment. Based in Munich, the company was founded in 1917. It produces professional motion picture cameras, lenses, lighting and post-production equipment. Hermann Simon menti ...
have been developing digital sensors capable of a higher dynamic range. RED EPIC-X can capture time-sequential HDRx images with a user-selectable 1–3 stops of additional highlight latitude in the "x" channel. The "x" channel can be merged with the normal channel in post production software. The
Arri Alexa The Arri Alexa (stylised as ΛLEXΛ) is a digital motion picture camera system developed by Arri. First introduced in April 2010, the camera was Arri's first major transition into digital cinematography after previous efforts such as the Arri ...
camera uses a dual-gain architecture to generate an HDR image from two exposures captured at the same time. With the advent of low-cost consumer digital cameras, many amateurs began posting tone-mapped HDR
time-lapse Time-lapse photography is a technique in which the frequency at which film frames are captured (the frame rate) is much lower than the frequency used to view the sequence. When played at normal speed, time appears to be moving faster and thus ...
videos on the Internet, essentially a sequence of still photographs in quick succession. In 2010, the independent studio Soviet Montage produced an example of HDR video from disparately exposed video streams using a
beam splitter A beam splitter or ''beamsplitter'' is an optical device that splits a beam of light into a transmitted and a reflected beam. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding wide ...
and consumer grade HD video cameras. Similar methods have been described in the academic literature in 2001 and 2007. In 2005,
Adobe Systems Adobe Inc. ( ), originally called Adobe Systems Incorporated, is an American multinational computer software company incorporated in Delaware and headquartered in San Jose, California. It has historically specialized in software for the crea ...
introduced several new features in
Photoshop CS2 Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Windows and macOS. It was originally created in 1988 by Thomas and John Knoll. Since then, the software has become the industry standard not only in raster ...
including ''Merge to HDR'', 32 bit floating point image support, and HDR tone mapping. On June 30, 2016, Microsoft added support for the digital compositing of HDR images to Windows 10 using the Universal Windows Platform.


See also

*
Comparison of graphics file formats This is a comparison of image file formats (graphics file formats). This comparison primarily features file formats for 2D images. General Ownership of the format and related information. Technical details See also * List of codecs Refer ...
* HDRi (data format) * High-dynamic-range rendering *
High-dynamic-range television High-dynamic-range television (HDR or HDR-TV) is a technology that improves the quality of display signals. It is contrasted with the retroactively-named standard dynamic range (SDR). HDR changes the way the luminance and colors of videos and ...
*
JPEG XT JPEG XT (ISO/IEC 18477) is an image compression standard which specifies backward-compatible extensions of the base JPEG standard (ISO/IEC 10918-1 and ITU Rec. T.81). JPEG XT extends JPEG with support for higher integer bit depths, high dynami ...
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Logluv TIFF Logluv TIFF is an encoding used for storing high-dynamic-range imaging data inside a TIFF image. It was originally developed by Greg Ward for storing HDR-output of his Radiance-photonmapper at a time where storage space was a crucial factor. Its im ...
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RGBE image format RGBE or Radiance HDR is an image format invented by Gregory Ward Larson for the Radiance rendering system. It stores pixels as one byte each for RGB (red, green, and blue) values with a one byte shared exponent. Thus it stores four bytes per pix ...
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scRGB scRGB is a wide color gamut RGB color space created by Microsoft and HP that uses the same color primaries and white/black points as the sRGB color space but allows coordinates below zero and greater than one. The full range is −0.5 through j ...
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Wide dynamic range In photography and videography, multi-exposure HDR capture is a technique that creates extended or high dynamic range (HDR) images by taking and combining multiple exposures of the same subject matter at different exposure levels. Combining m ...


References

* Benjamin Sarao (1999). Ben Sarao, Trenton, NJ, USA: ''Space Shuttle Discovery'', pages 16–17 (English ed.). Victor Hasselblad AB, Goteborg, Sweden. ISSN 0282-5449


External links

* {{Display technology Articles containing video clips Computer graphics High dynamic range High-dynamic-range imaging Photographic techniques