This article is about the
transfer functions used in
pictures
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-dimensiona ...
and
videos
Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...
and describing the relationship between
electrical 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'' ...
, scene light and displayed light.
Definition
The opto-electronic transfer function (OETF) is the
transfer function
In engineering, a transfer function (also known as system function or network function) of a system, sub-system, or component is a function (mathematics), mathematical function that mathematical model, theoretically models the system's output for ...
having the scene light as input and converting into the picture or video signal as output. This is typically done within a
camera
A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...
.
The electro-optical transfer function (EOTF) is the
transfer function
In engineering, a transfer function (also known as system function or network function) of a system, sub-system, or component is a function (mathematics), mathematical function that mathematical model, theoretically models the system's output for ...
having the picture or video signal as input and converting it into the linear light output of the display.
This is done within the display device.
The opto-optical transfer function (OOTF) is the
transfer function
In engineering, a transfer function (also known as system function or network function) of a system, sub-system, or component is a function (mathematics), mathematical function that mathematical model, theoretically models the system's output for ...
having the scene light as input and the displayed light as output. The OOTF is the result of the OETF and the EOTF and is usually non-
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 r ...
.
List of transfer functions
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 r ...
*
Raw formats
*Some OETF and EOTF have an initial
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 r ...
portion followed by a non-linear part (e.g.
sRGB
sRGB is a standard RGB (red, green, blue) color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the International Electrotechnical Commission ( ...
and
Rec.709).
Gamma
Gamma (uppercase , lowercase ; ''gámma'') is the third letter of the Greek alphabet. In the system of Greek numerals it has a value of 3. In Ancient Greek, the letter gamma represented a voiced velar stop . In Modern Greek, this letter re ...
*
Rec. 601
ITU-R Recommendation BT.601, more commonly known by the abbreviations Rec. 601 or BT.601 (or its former name CCIR 601) is a standard originally issued in 1982 by the CCIR (an organization, which has since been renamed as the Internatio ...
,
Rec. 709
Rec. 709, also known as Rec.709, BT.709, and ITU 709, is a standard developed by ITU-R for image encoding and signal characteristics of high-definition television.
The most recent version is BT.709-6 released in 2015. BT.709-6 defines the P ...
and
Rec. 2020
ITU-R Recommendation BT.2020, more commonly known by the abbreviations Rec. 2020 or BT.2020, defines various aspects of ultra-high-definition television (UHDTV) with standard dynamic range (SDR) and wide color gamut (WCG), including picture ...
: The
ITU-R
The ITU Radiocommunication Sector (ITU-R) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU) and is responsible for radio communications.
Its role is to manage the international radio-frequency sp ...
recommendations BT.601, BT.709 and BT.2020 describe the reference OETF of respectively
SD-TV,
HD-TV
High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the g ...
and
UHD-TV.
They are identical OETF based on a
gamma curve
Gamma correction or gamma is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. Gamma correction is, in the simplest cases, defined by the following power-law expression:
: V_\text = ...
and used for
SDR-TV.
*
BT.1886: The ITU-R Recommendation BT.1886 is the reference EOTF of
Standard Dynamic Range TV (SDR).
*
sRGB
sRGB is a standard RGB (red, green, blue) color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the International Electrotechnical Commission ( ...
: sRGB defines a transfer function based on a gamma curve and used for monitors, printers, and the
Web
Web most often refers to:
* Spider web, a silken structure created by the animal
* World Wide Web or the Web, an Internet-based hypertext system
Web, WEB, or the Web may also refer to:
Computing
* WEB, a literate programming system created by ...
. sRGB is standardized as IEC 61966-2-1:1999
Logarithmic
*
S-Log: Developed by
Sony
, commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professional ...
for
digital cameras
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
in order to increase captured
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-1 ...
*
Canon Log: Developed by
Canon
Canon or Canons may refer to:
Arts and entertainment
* Canon (fiction), the conceptual material accepted as official in a fictional universe by its fan base
* Literary canon, an accepted body of works considered as high culture
** Western can ...
for
digital cameras
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
in order to increase captured
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-1 ...
*Arri Log C: Developed by Arri for
digital cameras
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
in order to increase captured
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-1 ...
HDR
These transfer functions have been developed to allow
HDR display:
*
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 is a transfer function developed by
Dolby
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 ...
for
HDR and allowing a
luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls withi ...
level of up to 10,000
cd/m2. It is standardized in
Rec. 2100
ITU-R Recommendation BT.2100, more commonly known by the abbreviations Rec. 2100 or BT.2100, introduced high-dynamic-range television (HDR-TV) by recommending the use of the perceptual quantizer (PQ) or hybrid log–gamma (HLG) transfer func ...
and also as SMPTE ST 2084.
*
Hybrid log–gamma
The hybrid log–gamma (HLG) transfer function is a transfer function jointly developed by the BBC and NHK for high dynamic range (HDR) display. It's backward compatible with the transfer function of SDR (the gamma curve). It was approved as ARIB S ...
: HLG is a transfer function developed by
NHK
, also known as NHK, is a Japanese public broadcaster. NHK, which has always been known by this romanized initialism in Japanese, is a statutory corporation funded by viewers' payments of a television license fee.
NHK operates two terrestr ...
and
BBC #REDIRECT BBC #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board ex ...
for
HDR and offering some
backward compatibility
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
on
SDR displays. HLG is a hybrid transfer function in which the lower half of the signal values use a
gamma curve
Gamma correction or gamma is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. Gamma correction is, in the simplest cases, defined by the following power-law expression:
: V_\text = ...
and the upper half of the signal values use a
logarithmic curve
In mathematics, logarithmic growth describes a phenomenon whose size or cost can be described as a logarithm function of some input. e.g. ''y'' = ''C'' log (''x''). Note that any logarithm base can be used, since one can be converte ...
.
It is standardized in
Rec. 2100
ITU-R Recommendation BT.2100, more commonly known by the abbreviations Rec. 2100 or BT.2100, introduced high-dynamic-range television (HDR-TV) by recommending the use of the perceptual quantizer (PQ) or hybrid log–gamma (HLG) transfer func ...
.
References
{{Reflist
Transfer functions
Video
Imaging