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Lev Vygotsky

Lev Semyonovich Vygotsky (Лев Семёнович Выготский, ; Леў Сямёнавіч Выгоцкі; November 17 1896 – June 11, 1934) was a Russian and Soviet psychologist, best known for his work on psychological development in children and creating the framework known as cultural-historical activity theory. After his early death, his books and research were banned in the Soviet Union until Joseph Stalin's death in 1953, with a first collection of major texts published in 1956.

His major ideas include:

The Social Origin of Mind: Vygotsky believed that human mental and cognitive abilities are not biologically determined, but instead created and shaped by use of language and tools in the process of interacting and constructing the cultural and social environment.

The Importance of Mediation: He saw mediation as the key to human development, because it leads to the use of cultural tools and becomes a pathway for psychological development through the process of interiorization.

The Zone of Proximal Development: Vygotsky introduced the concept of the ZPD which refers to the gap between a child's current level of development and the level they are capable of reaching with tools provided by others with more knowledge.

The Significance of Play: Vygotsky viewed play as a crucial aspect of children's development, as the best sandbox to build and develop practice of mediation.

Biography
Lev Simkhovich Vygodsky (his patronymic was later changed to Semyonovich and his surname to Vygotsky for unclear reasons) was born on November 17, 1896, in the town of Orsha in Mogilev Governorate of the Russian Empire (now Belarus) into a non-religious middle-class family of Russian Jewish extraction. His father Simkha Leibovich (also known as Semyon Lvovich) was a banker and his mother was Tsetsilia Moiseevna.

Vygotsky was raised in the city of Gomel, where he was homeschooled until 1911 and then obtained a formal degree with distinction in a private Jewish gymnasium, which allowed him entrance to a university. In 1913, Vygotsky was admitted to the Moscow University by mere ballot through a "Jewish Lottery": at the time a three percent Jewish student quota was administered for entry in Moscow and Saint Petersburg universities. He had an interest in the humanities and social sciences, but at the insistence of his parents he applied to the medical school at Moscow University. During the first semester of study, he transferred to the law school. In parallel, he attended lectures at Shanyavsky Moscow City People's University. Vygotsky's early interests were in the arts and, primarily, in the topics of the history of the Jewish people, the tradition, culture and Jewish identity.

In January 1924, Vygotsky took part in the Second All-Russian Psychoneurological Congress in Petrograd (soon thereafter renamed Leningrad). After the Congress, Vygotsky met with Alexander Luria and with his help received an invitation to become a research fellow at the Psychological Institute in Moscow which was under the direction of Konstantin Kornilov. Vygotsky moved to Moscow with his new wife, Roza Smekhova, with whom he would have two children. He began his career at the Psychological Institute as a "staff scientist, second class". He also became a secondary school teacher, covering a period marked by his interest in the processes of learning and the role of language in learning.

By the end of 1925, Vygotsky completed his dissertation titled "The Psychology of Art", which was not published until the 1960s, and a book titled "Pedagogical Psychology", which apparently drew on lecture notes he prepared in Gomel while he was a psychology instructor at local educational establishments. In the summer of 1925 he made his first and only trip abroad to a London congress on the education of the deaf. Upon return to the Soviet Union, he was hospitalized due to tuberculosis and would remain an invalid and out of work until the end of 1926. His dissertation was accepted as the prerequisite of a scholarly degree, which was awarded to Vygotsky in autumn 1925 in absentia.

After his release from the hospital, Vygotsky did theoretical and methodological work on the crisis in psychology, but never finished the draft of the manuscript and interrupted his work on it around mid-1927. The manuscript was published later with notable editorial interventions and distortions in 1982 and was presented by the editors as one of the most important of Vygotsky's works. In this early manuscript, Vygotsky argued for the formation of a general psychology that could unite the naturalist objectivist strands of psychological science with the more philosophical approaches of Marxist orientation. However, he also harshly criticized those of his colleagues who attempted to build a "Marxist Psychology" as an alternative to the naturalist and philosophical schools. He argued that if one wanted to build a truly Marxist Psychology, there were no shortcuts to be found by merely looking for applicable quotes in the writings of Marx. Rather one should look for a methodology that was in accordance with the Marxian spirit.

From 1926 to 1930, Vygotsky worked on a research program investigating the development of higher psychological functions, i.e. culturally governed lower psychological functions such as voluntary attention, selective memory, object-oriented action, and decision making. During this period he gathered a group of collaborators including Alexander Luria, Boris Varshava, Alexei Leontiev, Leonid Zankov, and several others. Vygotsky guided his students in researching this phenomenon from three different perspectives:
 * The instrumental approach, which aimed to understand the ways humans use objects as mediation aids in memory and reasoning.
 * A developmental approach, focused on how children acquire higher cognitive functions during development
 * A culture-historical approach, studying how social and cultural patterns of interaction shape forms of mediation and developmental trajectories

Vygotsky died of a relapse of tuberculosis on June 11, 1934, at the age of 37, in Moscow. One of Vygotsky's last private notebook entries was:

"This is the final thing I have done in psychology – and I will like Moses die at the summit, having glimpsed the promised land but without setting foot on it. Farewell, dear creations. The rest is silence."

Chronology of the most important events of life and career
1922-24 - worked in the psychological laboratory which he organized in Gomel Pedagogical College;

January of 1924 - meeting Luria at the II Psychoneurological Congress in Petrograd, moving from Gomel to Moscow, enrolling in graduate school and taking position at the State Institute of Experimental Psychology in Moscow;

July of 1924 - the beginning of work as the head of the sub-department of the education of physically and intellectually disabled children in the department of social and legal protection of minors (SPON);

November of 1924 - during II Congress of the Social and Legal Protection of Minors in Moscow, a turn of Soviet defectology to social education was officially announced and collection of articles and materials edited by Vygotsky "Issues of the upbringing of blind, deaf and mentally retarded children" was published;

May 9, 1925 - the birth of the first child: the daughter Gita

Summer of 1925 - the only trip abroad: went to London for a defectology conference; on the way passed through Germany, where he met with German psychologists

November 5, 1925 - Vygotsky, in absence (due to illness), was awarded the title of senior researcher, equivalent to the modern degree of candidate of sciences for defense of the dissertation "Psychology of Art". The contract for the publication of The Psychology of Art was signed on November 9, 1925, but the text was published only in 1965;

November 21, 1925 to May 22, 1926 - hospitalization in the Zakharyino sanatorium-type hospital due to tuberculosis; upon discharge qualified as a disabled person until the end of the year;

1926 - Vygotsky's first book, Pedagogical Psychology, was published; writes notes and essays that would be published years later under the title "The Historical Meaning of the Psychological Crisis";

1927 - resumes work at the RANION Institute of Experimental Psychology and in a number of other institutions in Moscow and Leningrad;

September 17, 1927 - approved as a professor by the scientific and pedagogical section of the State Academic Council (SUS);

December 19, 1927 - appointed as the head of the Medical and Pedagogical Station of the Glavsotsvos of the People's Commissariat of Education of the RSFSR, remained in this position until October 1928 (dismissed on his own will);

December 28, 1927 to January 4, 1928 - First All-Russian Pedological Congress, Moscow: Vygotsky works as co-editor of the section on difficult childhood, and also presents two reports: "The development of a difficult child and its study" and "Instrumental method in pedology"; these two articles together with Zankov's report "Principles for the construction of complex programs of an auxiliary school from a pedological point of view" and Luria "On the methodology of instrumental-psychological research" become the first public presentation of "Instrumental Psychology" as a research method associated with the names of Vygotsky and Luria;

1928 - Vygotsky's second book "Pedology of School Age" was published, along with a number of articles establishing "Instrumental Psychology" approach in Russian and English language journals;

December of 1928 - after a conflict with the director of the Institute of Experimental Psychology (GIEP) K. N. Kornilov, the research activities of the Vygotsky-Luria group were curtailed in this organization, and experimental research was transferred to the Academy of Communications.

1929 - freelance scientific consultant, head of psychological laboratories at the Experimental Defectological Institute (transformed Medical-pedagogical station)

Major themes of research
Vygotsky was a pioneering psychologist with interests in extremely diverse fields: his work covered topics such as the origin and the psychology of art, development of higher mental functions, philosophy of science and the methodology of psychological research, the relation between learning and human development, concept formation, interrelation between language and thought development, play as a psychological phenomenon, learning disabilities, and abnormal human development (aka defectology). His philosophical framework includes interpretations of the cognitive role of mediation tools, as well as the re-interpretation of well-known concepts in psychology such as internalization of knowledge. Vygotsky introduced the notion of zone of proximal development, a metaphor capable of describing the potential of human cognitive development.

His most important and widely known contribution is his theory for the development of "higher psychological functions," which emerge through unification of interpersonal connections and actions taken within a given socio-cultural environment (i.e. language, culture, society, and tool-use). It was during this period that he identified the play of young children as their "leading activity", which he understood to be the main source of preschoolers' psychological development, and which he viewed as an expression of an inseparable unity of emotional, volitional, and cognitive development.

While Vygotsky never met Jean Piaget, he had read a number of his works and agreed on some of his perspectives on learning. At some point (around 1929–30), Vygotsky came to disagree with Piaget's understanding of learning and development, and held a different theoretical position from Piaget on the topic of inner speech; Piaget thought that egocentric speech follows from inner speech and "dissolved away" as children matured. Vygotsky showed that egocentric speech became inner speech, and then called "thoughts". Piaget only read Vygotsky's work after his death and openly praised him for his discovery of the social origin of children's thoughts, reasoning, and moral judgements.

Cultural-historical theory
The hypothesis put forward by Vygotsky was a paradigm shift in psychology. He was first to propose that all psychological functions that govern mental, cognitive and physical actions of the individual are not immutable but have a history of cultural development (in human history and in everyone personally) through interiorization of cultural tools. Therefore, the process of transformation which is happening when current cultural tools are interiorized becomes the focus of psychological research.

"It was assumed before, that individual possess function in well done, half-done or raw form, that function would unfold in the society, become complex, bigger, is enriched or, vice versa - slowed down and suppressed etc. Now we have reasons to believe that in regard of higher mental functions things are opposite. Functions first appear in social group in form of social relations of a child, then they become mental functions of an individual. For example, assumption was that every child is able to think, make arguments and proofs and look for sound reasonings. Debates with others grow from collision of these reasonings. But things are different. Research shows - debates foster thinking. Research also leads us to the same conclusions in regard to all other mental functions."

Vygotsky posits the existence of lower and higher mental functions. The latter have social origins and complex system structure, mediated by cultural tools and controlled by an individual. Vygotsky came to the conclusion that consciousness is possible because of the mediated nature of higher psychological functions. Between the stimulus and the reaction of a person (both behavioral and mental), an additional connection arises through a mediating link - a stimulus-means, or a sign. Signs are tools that mediate higher psychological functions and control one's own behavior. A word could direct attention, create personal meaning, form a concept and coordinate.

Vygotsky illustrated his idea of mediation via Buridan's ass paradox. A problematic situation of choosing between two equal possibilities, interested Vygotsky primarily from the point of view of solving it through a coin flip - redelegating decision to the outside object - an example of using cultural tools to govern one's own psychological function of volition.

While developing a method for studying higher psychological functions, Vygotsky was guided by the principle of ex ungue leonem and additionally analyzed phenomena such as using a knot in the handkerchief for remembering and finger counting.

Cultural mediation and internalization
Vygotsky studied child development and the significant roles of cultural mediation and interpersonal communication. He observed how higher mental functions developed through these interactions, and also represented the shared knowledge of a culture. This process is known as internalization. Internalization may be understood in one respect as "knowing how". For example, the practices of riding a bicycle or pouring a cup of milk, initially, are outside and beyond the child. The mastery of the skills needed for performing these practices occurs through the activity of the child within society. A further aspect of internalization is appropriation, in which children take tools and adapt them to personal use, perhaps using them in unique ways. Internalizing the use of a pencil allows the child to use it very much for personal ends rather than drawing exactly what others in society have drawn previously:

"The child acts and speaks at the same time, both are intertwined in one continuous operation for him. In this way, a blend of speech and action arises, a peculiar mixture from an adult's point of view, but a completely natural state for the child, who from the very first days of life, due to his helplessness, finds himself in conditions where the path from him to things and from things to him goes through another person."

Zone of Proximal Development
"Zone of Proximal Development" (ZPD) is a term Vygotsky used to characterize an individual's mental development. He originally defined the ZPD as "the distance between the actual developmental level as determined by independent problem solving and the level of potential development as determined through problem solving under adult guidance or in collaboration with more capable peers." He used the example of two children in school who originally could solve problems at an eight-year-old developmental level (that is, typical for children who were age 8). After each child received assistance from an adult, one was able to perform at a nine-year-old level and one was able to perform at a twelve-year-old level. He said "This difference between twelve and eight, or between nine and eight, is what we call the zone of proximal development." He further said that the ZPD "defines those functions that have not yet matured but are in the process of maturation, functions that will mature tomorrow but are currently in an embryonic state." The zone is bracketed by the learner's current ability and the ability they can achieve with the aid of an instructor of some capacity.

Scaffolding
According to Vygotsky, through the assistance of a more knowledgeable other, a child is able to learn skills or aspects of a skill that go beyond the child's actual developmental or maturational level. This assistance is defined as 'scaffolding'. The lower limit of ZPD is the level of skill reached by the child working independently (also referred to as the child's developmental level). The upper limit is the level of potential skill that the child is able to reach with the assistance of a more capable instructor. In this sense, the ZPD provides a prospective view of cognitive development, as opposed to a retrospective view that characterizes development in terms of a child's independent capabilities. The advancement through and attainment of the upper limit of the ZPD is limited by the instructional and scaffolding-related capabilities of the more knowledgeable other (MKO). The MKO is typically assumed to be an older, more experienced teacher or parent, but often can be a learner's peer or someone their junior. The MKO need not even be a person, it can be a machine or book, or other source of visual and/or audio input.

Thinking and Speech
In the last years of his life, Vygotsky paid most of his attention to the study of the relationship between thought and word in the structure of consciousness. This problem was explored in Vygotsky's book, Thinking and Speech, that was published posthumously in 1934. The book was a collection of essays and scholarly papers that Vygotsky wrote during different periods of his thought development. It was edited by his closest associates Kolbanovskii, Zankov, and Shif. The book established the connection between speech and the development of mental concepts and awareness. Vygotsky described silent inner speech as being qualitatively different from verbal external speech, but both equally important. Vygotsky believed inner speech developed from external speech via a gradual process of "internalization" (i.e., transition from the external to the internal), with younger children only really able to "think out loud". He claimed that in its mature form, inner speech would not resemble spoken language as we know it (in particular, being greatly compressed). Hence, thought itself developed socially.

Inner speech, according to Vygotsky, develops through the accumulation of long-term functional and structural changes. It branches off from the child's external speech along with the differentiation of the social and egocentric functions of speech, and, finally, the speech functions acquired by the child become the main functions of his thinking.

In this work, Vygotsky points out the genesis of the development of thinking and speech and that the relationship between them is not a constant value.

"But since we wanted to express all this in one short formula, in one sentence, we might put it thus: if at the beginning of development there stands the act, independent of the word, then at the end of it there stands the word which becomes the act, the word which makes man's action free."

Soviet Union
After Vygotsky's early death, his books and research were banned until Stalin's death in 1953, with a first collection of major texts published in 1956. A small group of his collaborators and students were able to continue his lines of thought in research. The members of the group laid a foundation for the systematic development of Vygotskian psychology in such diverse fields as the psychology of memory (P. Zinchenko), perception, sensation, and movement (Zaporozhets, Asnin, A. N. Leont'ev), personality (Lidiya Bozhovich, Asnin, A. N. Leont'ev), will and volition (Zaporozhets, A. N. Leont'ev, P. Zinchenko, L. Bozhovich, Asnin), psychology of play (G. D. Lukov, Daniil El'konin) and psychology of learning (P. Zinchenko, L. Bozhovich, D. El'konin), as well as the theory of step-by-step formation of mental actions (Pyotr Gal'perin), general psychological activity theory (A. N. Leont'ev) and psychology of action (Zaporozhets). Andrey Puzyrey elaborated the ideas of Vygotsky in respect of psychotherapy and even in the broader context of deliberate psychological intervention (psychotechnique), in general.

United States
Only a couple of Vygotsky's texts were published in English before the translation of Thinking and Speech in 1962. Since then, the majority of his texts have been translated, and his ideas have become influential in some modern educational approaches. The first proponents of Vygotsky in the USA were Michael Cole and James Wertsch. Today, an umbrella term for theoretical framework based on Vygotsky's ideas is "Cultural-historical activity theory" (aka CHAT) or "Activity theory".

Works

 * Consciousness as a problem in the Psychology of Behavior, 1925
 * Educational Psychology, 1926
 * Historical meaning of the crisis in Psychology, unfinished and aborted in 1927
 * The Problem of the Cultural Development of the Child, 1929
 * The Fundamental Problems of Defectology, 1929
 * The Socialist alteration of Man, 1930
 * Ape, Primitive Man, and Child: Essays in the History of Behaviour, A. R. Luria and L. S. Vygotsky, 1930
 * Tool and symbol in child development, c. 1930
 * Paedology of the Adolescent, 1929-1931
 * Play and its role in the Mental development of the Child, oral presentation 1933
 * Thinking and Speech, 1934
 * The Psychology of Art, 1971 (English translation by MIT Press)
 * Mind in Society: The Development of Higher Psychological Processes, 1978 (Harvard University Press)
 * The Collected Works of L. S. Vygotsky, 1987

title: Lev Vygotsky


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Y′UV

Y′UV, also written YUV, is the color model found in the PAL analogue color TV standard (excluding PAL-N). A color is described as a Y′ component (luma) and two chroma components U and V. The prime symbol (') denotes that the luma is calculated from gamma-corrected RGB input and that it is different from true luminance. Today, the term YUV is commonly used in the computer industry to describe colorspaces that are encoded using YCbCr.

In TV formats, color information (U and V) was added separately via a subcarrier so that a black-and-white receiver would still be able to receive and display a color picture transmission in the receiver's native black-and-white format, with no need for extra transmission bandwidth.

As for etymology, Y, Y′, U, and V are not abbreviations. The use of the letter Y for luminance can be traced back to the choice of XYZ primaries. This lends itself naturally to the usage of the same letter in luma (Y′), which approximates a perceptually uniform correlate of luminance. Likewise, U and V were chosen to differentiate the U and V axes from those in other spaces, such as the x and y chromaticity space. See the equations below or compare the historical development of the math.

Related color models
The scope of the terms Y′UV, YUV, YCbCr, YPbPr, etc., is sometimes ambiguous and overlapping.

 * Y′UV is the separation used in PAL.
 * Y'PbPr is the separation used in component video.
 * Y′CbCr is any digital encoding of Y'PbPr suited for video and image compression and transmission formats such as MPEG and JPEG.
 * YDbDr is the format used in SECAM and PAL-N, unusually based on non-gamma-corrected (linear) RGB, making the Y component true luminance.
 * Y′IQ is the format used in NTSC television.

All these formats are based on a luma component and two chroma components describing the color difference from gray. In all formats other than Y′IQ, each chroma component is a scaled version of the difference between red/blue and Y; the main difference lies in the scaling factors used, which is determined by color primaries and the intended numeric range (compare the use of Umax and Vmax in with a fixed $1⁄2$ in ). In Y′IQ, the UV plane is rotated by 33°.

History
Y′UV was invented when engineers wanted color television in a black-and-white infrastructure. They needed a signal transmission method that was compatible with black-and-white (B&W) TV while being able to add color. The luma component already existed as the black and white signal; they added the UV signal to this as a solution.

The UV representation of chrominance was chosen over straight R and B signals because U and V are color difference signals. In other words, the U and V signals tell the television to shift the color of a certain spot without altering its brightness. Or the U and V signals tell the monitor to make one color brighter at the cost of the other and by how much it should be shifted. The higher (or the lower when negative) the U and V values are, the more saturated (colorful) the spot gets. The closer the U and V values get to zero, the lesser it shifts the color meaning that the red, green and blue lights will be more equally bright, producing a grayer spot. This is the benefit of using color difference signals, i.e. instead of telling how much red there is to a color, it tells by how much it is more red than green or blue. In turn this meant that when the U and V signals would be zero or absent, it would just display a grayscale image. If R and B were to have been used, these would have non-zero values even in a B&W scene, requiring all three data-carrying signals. This was important in the early days of color television, because old black and white TV signals had no U and V signals present, meaning the color TV would just display it as B&W TV out of the box. In addition, black and white receivers could take the Y′ signal and ignore the U- and V-color signals, making Y′UV backward-compatible with all existing black-and-white equipment, input and output. If the color-TV standard wouldn't have used color difference signals, it could mean a color TV would make funny colors out of a B&W broadcast or it would need additional circuitry to translate the B&W signal to color. It was necessary to assign a narrower bandwidth to the chrominance channel because there was no additional bandwidth available. If some of the luminance information arrived via the chrominance channel (as it would have if RB signals were used instead of differential UV signals), B&W resolution would have been compromised.

SDTV with BT.470
Y′UV signals are typically created from RGB (red, green and blue) source. Weighted values of R, G, and B are summed to produce Y′, a measure of overall brightness or luminance. U and V are computed as scaled differences between Y′ and the B and R values.

PAL (NTSC used YIQ, which is further rotated) standard defines the following constants, derived from BT.470 System M primaries and white point using SMPTE RP 177 (same constants called matrix coefficients were used later in BT.601, although it uses 1/2 instead of 0.436 and 0.615):

 * $$\begin{align}

W_R &= 0.299, \\ W_G &= 1 - W_R - W_B = 0.587, \\ W_B &= 0.114, \\ U_\text{max} &= 0.436, \\ V_\text{max} &= 0.615. \end{align}$$

PAL signals in Y′UV are computed from R'G'B' (only SECAM IV used linear RGB ) as follows:

 * $$\begin{align}

Y' &= W_R R' + W_G G' + W_B B' = 0.299 R' + 0.587 G' + 0.114 B', \\ U &= U_\text{max} \frac{B' - Y'}{1 - W_B} \approx 0.492(B' - Y'), \\ V &= V_\text{max} \frac{R' - Y'}{1 - W_R} \approx 0.877(R' - Y'). \end{align}$$

The resulting ranges of Y′, U, and V respectively are [0, 1], [−Umax, Umax], and [−Vmax, Vmax].

Inverting the above transformation converts Y′UV to RGB:

 * $$\begin{align}

R' &= Y' + V \frac{1 - W_R}{V_\text{max}} = Y' + \frac{V}{0.877} = Y' +  1.14 V,\\ G' &= Y' - U \frac{W_B (1 - W_B)}{U_\text{max} W_G} - V \frac{W_R (1 - W_R)}{V_\text{max} W_G} \\ &= Y' - \frac{0.232 U}{0.587} - \frac{0.341 V}{0.587} = Y' - 0.395 U - 0.581 V, \\ B' &= Y' + U \frac{1 - W_B}{U_\text{max}} = Y' + \frac{U}{0.492} = Y' +  2.033 U. \end{align}$$

Equivalently, substituting values for the constants and expressing them as matrices gives these formulas for BT.470 System M (PAL):

 * $$\begin{align}

\begin{bmatrix} Y' \\ U \\ V \end{bmatrix} &= \begin{bmatrix} 0.299  &  0.587   &  0.114 \\   -0.14713 & -0.28886 &  0.436 \\    0.615   & -0.51499 & -0.10001  \end{bmatrix} \begin{bmatrix} R' \\ G' \\ B' \end{bmatrix}, \\

\begin{bmatrix} R' \\ G' \\ B' \end{bmatrix} &= \begin{bmatrix} 1 & 0       &  1.13983 \\  1 & -0.39465 & -0.58060 \\  1 &  2.03211 &  0  \end{bmatrix} \begin{bmatrix} Y' \\ U \\ V \end{bmatrix}. \end{align}$$ For small values of Y' it is possible to get R, G, or B values that are negative so in practice we clamp the RGB results to the interval [0,1] or more correctly clamp inside the Y'CbCr.

In BT.470 a mistake was made because 0.115 was used instead of 0.114 for blue and 0.493 was the result instead of 0.492. In practice that did not affect the decoders because the approximation 1/2.03 was used.

HDTV with BT.709
For HDTV the ATSC decided to change the basic values for WR and WB compared to the previously selected values in the SDTV system. For HDTV these values are provided by Rec. 709. This decision further impacted on the matrix for the Y′UV↔RGB conversion so that its member values are also slightly different. As a result, with SDTV and HDTV there are generally two distinct Y′UV representations possible for any RGB triple: a SDTV-Y′UV and an HDTV-Y′UV one. This means in detail that when directly converting between SDTV and HDTV, the luma (Y′) information is roughly the same but the representation of the chroma (U & V) channel information needs conversion. Still in coverage of the CIE 1931 color space the Rec. 709 color space is almost identical to Rec. 601 and covers 35.9%. In contrast to this UHDTV with Rec. 2020 covers a much larger area and thus its very own matrix was derived for YCbCr (no YUV/Y′UV, since decommissioning of analog TV).

BT.709 defines these weight values:

 * $$\begin{align}

W_R &= 0.2126, \\ W_G &= 1 - W_R - W_B = 0.7152, \\ W_B &= 0.0722 \\ \end{align}$$ The Umax and Vmax values are from above.

The conversion matrices for analog form of BT.709 are these, but there is no evidence those were ever used in practice (instead only actually described form of BT.709 is used, the YCbCr form):

 * $$\begin{align}

\begin{bmatrix} Y' \\ U \\ V \end{bmatrix} &= \begin{bmatrix} 0.2126 &  0.7152  &  0.0722 \\   -0.09991 & -0.33609 &  0.436 \\    0.615   & -0.55861 & -0.05639  \end{bmatrix} \begin{bmatrix} R' \\ G' \\ B' \end{bmatrix} \\

\begin{bmatrix} R' \\ G' \\ B' \end{bmatrix} &= \begin{bmatrix} 1 & 0       &  1.28033 \\  1 & -0.21482 & -0.38059 \\  1 &  2.12798 &  0  \end{bmatrix} \begin{bmatrix} Y' \\ U \\ V \end{bmatrix} \end{align}$$

Luminance/chrominance systems in general
The primary advantage of luma/chroma systems such as Y′UV, and its relatives Y′IQ and YDbDr, is that they remain compatible with black and white analog television (largely due to the work of Georges Valensi). The Y′ channel saves all the data recorded by black and white cameras, so it produces a signal suitable for reception on old monochrome displays. In this case, the U and V are simply discarded. If displaying color, all three channels are used, and the original RGB information can be decoded.

Another advantage of Y′UV is that some of the information can be discarded in order to reduce bandwidth. The human eye has fairly little spatial sensitivity to color: the accuracy of the brightness information of the luminance channel has far more impact on the image detail discerned than that of the other two. Understanding this human shortcoming, standards such as NTSC and PAL reduce the bandwidth of the chrominance channels considerably. (Bandwidth is in the temporal domain, but this translates into the spatial domain as the image is scanned out.)

Therefore, the resulting U and V signals can be substantially "compressed". In the NTSC (Y′IQ) and PAL systems, the chrominance signals had significantly narrower bandwidth than that for the luminance. Early versions of NTSC rapidly alternated between particular colors in identical image areas to make them appear adding up to each other to the human eye, while all modern analogue and even most digital video standards use chroma subsampling by recording a picture's color information at reduced resolution. Only half the horizontal resolution compared to the brightness information is kept (termed 4:2:2 chroma subsampling), and often the vertical resolution is also halved (giving 4:2:0). The 4:x:x standard was adopted due to the very earliest color NTSC standard which used a chroma subsampling of 4:1:1 (where the horizontal color resolution is quartered while the vertical is full resolution) so that the picture carried only a quarter as much color resolution compared to brightness resolution. Today, only high-end equipment processing uncompressed signals uses a chroma subsampling of 4:4:4 with identical resolution for both brightness and color information.

The I and Q axes were chosen according to bandwidth needed by human vision, one axis being that requiring the most bandwidth, and the other (fortuitously at 90 degrees) the minimum. However, true I and Q demodulation was relatively more complex, requiring two analog delay lines, and NTSC receivers rarely used it.

However, this color modulation strategy is lossy, particularly because of crosstalk from the luma to the chroma-carrying wire, and vice versa, in analogue equipment (including RCA connectors to transfer a digital signal, as all they carry is analogue composite video, which is either YUV, YIQ, or even CVBS). Furthermore, NTSC and PAL encoded color signals in a manner that causes high bandwidth chroma and luma signals to mix with each other in a bid to maintain backward compatibility with black and white television equipment, which results in dot crawl and cross color artifacts. When the NTSC standard was created in the 1950s, this was not a real concern since the quality of the image was limited by the monitor equipment, not the limited-bandwidth signal being received. However today's modern television is capable of displaying more information than is contained in these lossy signals. To keep pace with the abilities of new display technologies, attempts were made since the late 1970s to preserve more of the Y′UV signal while transferring images, such as SCART (1977) and S-Video (1987) connectors.

Instead of Y′UV, Y′CbCr was used as the standard format for (digital) common video compression algorithms such as MPEG-2. Digital television and DVDs preserve their compressed video streams in the MPEG-2 format, which uses a fully defined Y′CbCr color space, although retaining the established process of chroma subsampling. Cinepak, a video codec from 1991, used a modified YUV 4:2:0 colorspace. The professional CCIR 601 digital video format also uses Y′CbCr at the common chroma subsampling rate of 4:2:2, primarily for compatibility with previous analog video standards. This stream can be easily mixed into any output format needed.

Y′UV is not an absolute color space. It is a way of encoding RGB information, and the actual color displayed depends on the actual RGB colorants used to display the signal. Therefore, a value expressed as Y′UV is only predictable if standard RGB colorants are used (i.e. a fixed set of primary chromaticities, or particular set of red, green, and blue).

Furthermore, the range of colors and brightnesses (known as the color gamut and color volume) of RGB (whether it be BT.601 or Rec. 709) is far smaller than the range of colors and brightnesses allowed by Y′UV. This can be very important when converting from Y′UV (or Y′CbCr) to RGB, since the formulas above can produce "invalid" RGB values – i.e., values below 0% or very far above 100% of the range (e.g., outside the standard 16–235 luma range (and 16–240 chroma range) for TVs and HD content, or outside 0–255 for standard definition on PCs). Unless these values are dealt with they will usually be "clipped" (i.e., limited) to the valid range of the channel affected. This changes the hue of the color, which is very undesirable, so it is therefore often considered better to desaturate the offending colors such that they fall within the RGB gamut. Likewise, when RGB at a given bit depth is converted to YUV at the same bit depth, several RGB colors can become the same Y′UV color, resulting in information loss.

Relation with Y′CbCr
Y′UV is often used as a term for YCbCr. However, while related, they are different formats with different scale factors; additionally, unlike YCbCr, Y’UV has historically used two different scale factors for the U component vs. the V component. Not scaled matrix is used in Photo CD's PhotoYCC. U and V are bipolar signals which can be positive or negative, and are zero for grays, whereas YCbCr usually scales all channels to either the 16–235 range or the 0–255 range, which makes Cb and Cr unsigned quantities which are 128 for grays.

Nevertheless, the relationship between them in the standard case is simple. In particular, the Y' channels of both are linearly related to each other, both Cb and U are related linearly to (B-Y), and both Cr and V are related linearly to (R-Y).

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title: Y′UV


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Phi Kappa Psi

Phi Kappa Psi (ΦΚΨ), commonly known as Phi Psi, is an American collegiate social fraternity that was founded at Jefferson College in Canonsburg, Pennsylvania in 1852. The fraternity has over ninety chapters at accredited four-year colleges and universities throughout the United States. More than 179,000 men have been initiated into Phi Kappa Psi since its founding. Phi Kappa Psi and Phi Gamma Delta, both founded at the same college, form the Jefferson Duo.

History
In the winter of 1850, a typhoid fever epidemic hit Jefferson College in Canonsburg, Pennsylvania. Many students left school. Among those who remained were William Henry Letterman and Charles Page Thomas Moore. They chose to care for their classmates who were stricken with the contagious disease, and a strong bond was formed.

The following school year, Letterman and Moore decided to found a fraternity based on "the great joy of serving others" that they experienced during the epidemic. Letterman and Moore founded Phi Kappa Psi in Widow Letterman's home on the campus of Jefferson College in Canonsburg, Pennsylvania on February 19, 1852.

The fraternity's first Grand Arch Council convened in 1853 in Charlottesville, Virginia. At the 1885 Grand Arch Council in Columbus, Ohio, a special committee was created to draft a new constitution. The fraternity also decided to prohibit chapters from honorary initiations. The new constitution was ratified at the 1886 Grand Arch Council in Indianapolis, Indiana.

In 1894 in New York City, the Arch Grand Council passed a resolution to oppose hazing for its undergraduate members, becoming the first fraternity to publicly oppose hazing. The Arch Grand Council adopted the Phi Kappa Psi Creed in 1964.

Symbols
The coat of arms as adopted in 1908 has a sable (black) field, but today it is most often seen as shown in the adjacent infobox. The fraternity's official colors are Cardinal Red and Hunter Green. The badge is a textured bordered shield with a lamp resting on a book at the bottom and an eye surrounded by two stars at the top. In the center of the shield are the Greek letters Φ, Κ, and Ψ.

The fraternity flag is in the proportions of eight and one-half feet wide by six feet high; it was designed in 1916 following instructions from the Grand Arch Council.

The colors are the official fraternity colors and the design is three vertical stripes of equal width, a hunter green in the middle, flanked on either side by a cardinal red stripe. A smaller version is available with proportions roughly three and one-half feet wide by two feet high. The fraternity song is "Amici". Its root dates back to the traditional song "Annie Lisle".

Executive Council
The Executive Council of Phi Kappa Psi is composed of the President, Vice President, Secretary, Treasurer, and six Archons. Since its founding, Phi Kappa Psi has been controlled by undergraduates. This unique system of governance is achieved by a governing body, the Executive Council, which is made up of a majority of elected undergraduates. These undergraduates, known as Archons, represent the six Districts of Phi Kappa Psi, which divide the nation into roughly equal parts based on the number of chapters represented. Archons are elected during meetings of each District during District Councils, held during odd-numbered years. Four alumni also serve on the Executive Council and are elected at Grand Arch Councils, held during even-numbered years.

Grand Chapters
Phi Kappa Psi's first form of government centered on a Grand Chapter. One chapter at a time was designated the Grand Chapter, and it was responsible for governing the national fraternity. This lasted until 1886 when a new constitution changed to the current form of government.

In 1992, Phi Kappa Psi began to award one exceptional chapter with the Grand Chapter Award. Its name is derived from the fraternity's first form of government. This award was initially granted biennially at Grand Arch Councils. 2001 marked the first time that this award was granted in an odd-numbered year, and it has been an annual award ever since.

Grand Arch Councils
The supreme governing body of Phi Kappa Psi is the Grand Arch Council (G.A.C.). The first Grand Arch Council convened in 1853 in Charlottesville, Virginia. The council met at an irregular schedule until an entirely new form of government was ratified in 1886. Beginning in 1888, nearly all G.A.C.s have occurred biennially, except 1944 which was canceled due to World War II and 2020 which was canceled due to the COVID-19 epidemic.

The Order of the S.C.
The Order of the S.C. was formed in 1920 at the Grand Arch Council to recognize the most loyal of alumni. It regarded by Phi Kappa Psi as a "fraternity within a fraternity". Entrance can only be gained by performing, to the satisfaction of the Order, one or more acts of benefit to the fraternity and attending at least seven Grand Arch Councils. The Order meets every two years, during Phi Kappa Psi's biennial Grand Arch Council. The words which the initials "S.C." represent are held secret by its members.

Phi Kappa Psi Foundation
Organized in 1914, the Phi Kappa Psi Foundation is a 501(c)(3) nonprofit, public educational foundation. It funds scholarships, grants, fellowships, and assistantships for Phi Psis and other students across the country.

Chapters
The Phi Kappa Psi Fraternity is composed of chapters and alumni associations, the former of which is the scope of this section. Each chapter is chartered to an individual host institution. These host institutions must be accredited four-year degree-granting colleges and universities in a state, province, territory, or federal district of Canada or the United States. To date, chapter charters have only been granted to groups at U.S. institutions.

When Phi Kappa Psi is extending to an institution that does not currently have a chapter, a probationary group called a "colony" is formed. After the criteria are met, that colony receives its charter and becomes a chapter.

A chapter becomes inactive when it relinquishes its charter, or the charter is revoked by the fraternity, such as was the case with California Beta until its renewal.

Chapter naming convention
The chapter naming convention is composed of the top-level subnational division of that chapter's host institution, and a Greek letter in alphabetical order from when the charter was originally issued. For example, the first Phi Psi chapter is from Jefferson College in Canonsburg, Pennsylvania. The first letter in the Greek alphabet is Alpha. Hence, the chapter name is Pennsylvania Alpha. The second chapter, and the first in Virginia, was installed at the University of Virginia, so it is the Virginia Alpha chapter. The third chapter overall, and the second in Virginia, was installed at Washington & Lee University, so it is the Virginia Beta chapter. The George Washington University chapter is the only chapter ever chartered in the District of Columbia, so it is the District of Columbia Alpha chapter.

If borders change, the chapter name does not. Virginia Delta was chartered at Bethany College in 1859. After the Civil War, Bethany College was in West Virginia, but the chapter remained Virginia Delta.

Chapters are named based on when the charter is granted, not when it is installed. As a result, there have been rare instances when the chapter naming convention may not appear to be consistent with the charter dates. For example, four charters have been granted in Iowa; the second granted was the fourth installed, so Iowa Beta was installed after Iowa Gamma and Iowa Delta.

Membership
An active member of the fraternity is a full-time enrolled student at his chapter's host institution at the undergraduate, graduate, or post-graduate level; all others, including members who have graduated or transferred to a school without a Phi Psi chapter, are considered alumni. Men may be initiated into Phi Kappa Psi either by an active chapter, or as part of a colony that is being installed as a chapter. Members typically join Phi Kappa Psi when a chapter extends an offer to enter into a probationary period known as pledgeship, which within the organization, and per National guidelines lasts no more than 6 weeks and concludes with initiation.

Membership is normally only granted to men who are enrolled as full-time students at a chapter's host institution. There have been three exceptions to this:
 * 1. Alumni of a colony which became a chapter after their graduation, and for two years after.
 * 2. Men who have been of service to a chapter, but not students at the institution.
 * 3. Honorary membership extended to men of prominence, a practice that was banned in 1885.

Scandals and misconduct
Despite policies put in place by the national fraternity to curtail hazing and other abusive behavior,  Local chapters or members have occasionally been involved in events that lead to deaths or sexual assault. The following events have been cited as impacting chapters and their communities:

 * In 1984, Liz Seccuro was drugged and raped at the Phi Kappa Psi house on the University of Virginia campus. William Beebe, who was not a member of the fraternity, pled guilty to sexual battery in 2007, following a written confession he had made to Seccuro as part of his Alcoholics Anonymous program. Two others were implicated during an investigation of the Beebe case. They retained legal counsel and invoked the Fifth Amendment when questioned before a grand jury and were ultimately not charged.
 * In a 2009 incident, members were accused of stealing University of Arizona student newspapers that contained a news story about a student who alleged that she had been drugged with GHB and possibly raped while blacked out at a house party.  The homework of two chapter members was found at the same location where the stolen newspapers were discarded.   Emails from friends and relatives of Phi Kappa Psi members confirmed that the theft had been organized by the fraternity's leadership to stop the spreading of the allegations.
 * In 2013, West Virginia University placed its chapter on suspension following an alleged hazing incident. According to the Morgantown Police Department, a 19-year-old pledge was pushed against a wall and suffered a split chin and broken teeth while doing push-ups and other hazing rituals. After a joint investigation by both the university and the national fraternity, the chapter house was closed and the chapter was suspended for five semesters.
 * In 2014, Brown University suspended its Phi Kappa Psi chapter after two female students reported that they rapidly became intoxicated at the fraternity's party and tested positive for the date rape drug GHB. Chapter officials disputed the test results and a subsequent investigation by the university showed that the results were inconclusive for the presence of GHB due to errors in laboratory procedures. In 2016, the female students sued the university for intentionally mishandling the case because a Brown University trustee's son was accused of drugging them with plans to sexually assault them.
 * In 2017, Matthew Ellis, a Phi Kappa Psi pledge at Texas State University, attended a fraternity event and was found unresponsive in an off-campus apartment complex the next morning. Ellis' death led the university suspend all Greek activities on campus soon after. The chapter of Phi Kappa Psi at Texas State University had been put on suspension by the national organization a week earlier for unrelated violations. The local police placed the fraternity under investigation to determine the cause of his death.
 * In 2020, Cornell University "permanently revoked" recognition of its chapter of Phi Kappa Psi nearly a year after a freshman student was found dead in a gorge after leaving an illegal Christmas-themed "dirty rush" party in October 2019.

University of Virginia gang rape hoax
In a since-retracted November 2014 article in Rolling Stone, Sabrina Erdely reported in detail allegations of a 2012 gang rape, and reported in brief on allegations of two subsequent gang rapes at the University of Virginia. Following the story the fraternity voluntarily suspended activity there. Rolling Stone apologized for the article, and after investigating the accusations, Phi Kappa Psi, ABC News, and The Washington Post said they had found significant discrepancies in the account.

On January 12, the University of Virginia reinstated the Phi Kappa Psi fraternity after the police investigation concluded that no incident had occurred at the fraternity. On April 5, 2015, Rolling Stone formally retracted the story. Sabrina Erdely publicly apologized for the article on the same day. The next day, leaders of the Phi Kappa Psi chapter announced the fraternity would file a lawsuit against Rolling Stone over the article. Rolling Stone has settled the case and paid the Phi Kappa Psi chapter at the University of Virginia $1.65 million.

title: Phi Kappa Psi


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I'm a librarian for children and youth, a storyteller and amateur artist currently living in Pennsylvania.

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