Photopic (black) and scotopic^[1] (green) luminosity functions. The photopic includes the CIE 1931 standard^[2] (solid), the Judd–Vos 1978 modified data^[3] (dashed), and the Sharpe, Stockman, Jagla & Jägle 2005 data^[4] (dotted). The horizontal axis is wavelength in nm.

The candela ( /kænˈdɛlə/ or /kænˈdiːlə/; symbol: cd) is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function (a standardized model of the sensitivity of the human eye to different wavelengths, also known as the luminous efficiency function^[4][5]). A common candle emits light with a luminous intensity of roughly one candela. If emission in some directions is blocked by an opaque barrier, the emission would still be approximately one candela in the directions that are not obscured.

The word candela means candle in Latin, as well as in many modern languages.

Definition[link]

Like other SI base units, the candela has an operational definition—it is defined by a description of a physical process that will produce one candela of luminous intensity. Since the 16th General Conference on Weights and Measures (CGPM) in 1979, the candela has been defined as:^[6]

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×10¹² hertz and that has a radiant intensity in that direction of ¹⁄₆₈₃ watt per steradian.

The definition describes how to produce a light source that (by definition) emits one candela. Such a source could then be used to calibrate instruments designed to measure luminous intensity.

The candela is sometimes still called by the old name candle,^[7] such as in foot-candle and the modern definition of candlepower.

Explanation[link]

The frequency chosen is in the visible spectrum near green, corresponding to a wavelength of about 555 nanometers. The human eye is most sensitive to this frequency, when adapted for bright conditions. At other frequencies, more radiant intensity is required to achieve the same luminous intensity, according to the frequency response of the human eye. The luminous intensity for light of a particular wavelength λ is given by

Failed to parse (Missing texvc executable; please see math/README to configure.): I_\mathrm{v}(\lambda)= 683.002 \cdot \overline{y}(\lambda) \cdot I_\mathrm{e}(\lambda)

where I_v(λ) is the luminous intensity in candelas, I_e(λ) is the radiant intensity in W/sr and Failed to parse (Missing texvc executable; please see math/README to configure.): \textstyle \overline{y}(\lambda)

is the standard luminosity function. If more than one wavelength is present (as is usually the case), one must sum or integrate over the spectrum of wavelengths present to get the total luminous intensity.

Examples[link]

A common candle emits light with roughly 1 cd luminous intensity. A 25 W compact fluorescent light bulb puts out around 1700 lumens; if that light is radiated equally in all directions, it will have an intensity of around 135 cd. Focused into a 20° beam, it will have an intensity of around 18 000 cd.

The luminous intensity of light-emitting diodes is measured in millicandela (mcd), or thousandths of a candela. Indicator LEDs are typically in the 50 mcd range; "ultra-bright" LEDs can reach 15 000 mcd, or higher.

Origin[link]

Prior to 1948, various standards for luminous intensity were in use in a number of countries. These were typically based on the brightness of the flame from a "standard candle" of defined composition, or the brightness of an incandescent filament of specific design. One of the best-known of these was the English standard of candlepower. One candlepower was the light produced by a pure spermaceti candle weighing one sixth of a pound and burning at a rate of 120 grains per hour. Germany, Austria and Scandinavia used the Hefnerkerze, a unit based on the output of a Hefner lamp.^[8]

It became clear that a better-defined unit was needed. The Commission Internationale de l'Éclairage (International Commission on Illumination) and the CIPM proposed a “new candle” based on the luminance of a Planck radiator (a black body) at the temperature of freezing platinum. The value of the new unit was chosen to make it similar to the earlier unit candlepower. The decision was promulgated by the CIPM in 1946:

The value of the new candle is such that the brightness of the full radiator at the temperature of solidification of platinum is 60 new candles per square centimetre.^[9]

It was then ratified in 1948 by the 9th CGPM which adopted a new name for this unit, the candela. In 1967 the 13th CGPM removed the term "new candle" and gave an amended version of the candela definition, specifying the atmospheric pressure applied to the freezing platinum:

The candela is the luminous intensity, in the perpendicular direction, of a surface of 1 / 600 000 square metre of a black body at the temperature of freezing platinum under a pressure of 101 325 newtons per square metre.^[10]

In 1979, because of the difficulties in realizing a Planck radiator at high temperatures and the new possibilities offered by radiometry, the 16th CGPM adopted the modern definition of the candela.^[11] The arbitrary (1/683) term was chosen so that the new definition would exactly match the old definition. Although the candela is now defined in terms of the second (an SI base unit) and the watt (a derived SI unit), the candela remains a base unit of the SI system, by definition.^[12]

SI photometric light units[link]

Relationship between luminous intensity and luminous flux[link]

If a source emits a known luminous intensity I_v (in candelas) in a well-defined cone, the total luminous flux Φ_v in lumens is given by

Φ_v = I_v ⋅ 2π ⋅ (1 - cos(A/2)),

where A is the radiation angle of the lamp—the full vertex angle of the emission cone. For example, a lamp that emits 590 cd with a radiation angle of 40° emits about 223 lumens. See MR16 for emission angles of some common lamps.^[13][14]

If the source emits light uniformly in all directions, the flux can be found by multiplying the intensity by 4π: a uniform 1 candela source emits 12.6 lumens.

See also[link]

• New SI definitions

References[link]

v t e SI units Base units Ampere · Candela · Kelvin · Kilogram · Metre · Mole · Second Derived units Becquerel · Coulomb · Degree Celsius · Farad · Gray · Henry · Hertz · Joule · Katal · Lumen · Lux · Newton · Ohm · Pascal · Radian · Siemens · Sievert · Steradian · Tesla · Volt · Watt · Weber Accepted for use with SI Dalton (Atomic mass unit) · Astronomical unit · Day · Decibel · Degree Celsius · Degree of arc · Electronvolt · Hectare · Hour · Litre · Minute · Minute of arc · Neper · Second of arc · Tonne Atomic units · Natural units See also SI prefixes · Systems of measurement · Conversion of units · New SI definitions · History of the metric system Book:International System of Units  · Category:SI base units

Daddy Yankee
Background information
Birth name	Ramón Ayala
Also known as	Winchester 30-30 El Cangri El Jefe The Big Boss DY El Máximo Lider
Born	(1977-02-03) February 3, 1977 (age 35)
Origin	San Juan, Puerto Rico
Genres	Reggaeton, Latin rap, hip-hop
Years active	1992–present
Labels	El Cartel, Interscope, Sony Music Latin
Website	daddyyankee.com

Ramón Luis Ayala Rodríguez (born February 3, 1977), known artistically as Daddy Yankee, is a Latin Grammy Award-winning Puerto Rican reggaeton recording artist. Ayala was born in Río Piedras, the largest district of San Juan, where he became interested in music at a young age. In his youth he was interested in baseball, and aspired to become a Major League Baseball player. He was unable to continue this sport when he received an injury to one of his legs, leaving him unable to walk correctly. He then became involved in the underground rap movement that was in its early stages in Puerto Rico, later to be called reggaeton. After receiving lessons from several artists within the genre, he developed an independent career, first recording in a production titled Playero 37. After this he began to produce independent albums. His first solo album was No Mercy. He subsequently formed a duo with Nicky Jam, and then continued his solo career with the releases of El Cartel and El Cartel II. This led him be one of many pioneers of the reggaeton genre earning him the nickname "El Cangri".

In 2002 El Cangri.com became Ayala's first album with international success, receiving coverage in the markets of New York and Miami. Barrio Fino was released in 2004, and the album received numerous awards, including Lo Nuestro Awards and a Latin Billboard, as well as receiving nominations for the Latin Grammy and MTV Video Music Awards. Barrio Fino performed well in the sales charts of the United States, Latin America, Europe, and Japan. On June 5, 2007, El Cartel Records released El Cartel: The Big Boss, which was ranked as the top-selling album in Latin music genres in 2007. He promoted the album with an international tour which began in the United States and continued through Latin America, breaking attendance records in Ecuador and Bolivia.

His performances have appeared on more than 70 albums, including compilations such as Mas Flow 2 and Blin Blin Vol. 1. Outside of his work as a musician, Ayala has also worked as an actor and producer. Throughout his career, he has been generally reluctant to discuss his personal life, but has publicly expressed the importance of his wife and children to him.

Following the incident, he became interested in the underground movement, which at the time was in an early organizational stage.^[1] He also took more interest in the events that took place in the neighborhood in which he was raised, a public housing project named Villa Kennedy.^[2] Early in his career he attempted to imitate the style of Vico C. He went on to emulate other artists in the genre, including DJ Playero, DJ Nelson, and DJ Goldy, taking elements from their styles in order to develop an original style.^[1] In doing so, he eventually abandoned the traditional model of rap and became one of the first artists to perform reggaeton.^[1] Ayala first recorded with DJ Playero as a featured artist in a production titled Playero 37, which was released in 1992.^[2]

Musical career[link]

Independent productions[link]

His first album, titled No Mercy, was produced in 1995 when Ayala was eighteen years old.^[2] The production did not sell well, and he continued his work within the genre for the rest of the decade, eventually forming a duo with Nicky Jam. One of the duo's songs, "Posición", was included in the soundtrack of One Tough Cop, a movie directed by Bruno Barreto, that was released in 1998. Beginning in 2000, Ayala began concentrating more on his solo career, releasing albums produced outside studios. The first production he released was titled El Cartel, featuring elements of the mixtape style.^[2] In 2001 El Cartel II was released, a direct sequel to the previous production, and influenced by similar genres.

In 2005 El Cangri.com was released, and became the first album in Ayala's career to sell well outside Puerto Rico, mostly in the United States.^[2] The album was produced by VI Music, an independent recording studio in Puerto Rico, and was not supported by a major label.^[2] The most successful single from the album was "Latigazo", which received significant play on radio stations in New York and Miami.^[2] The album reached #43 on Billboard's Top Latin Albums chart.^[2] Following the release of this disc, Ayala performed at the Roberto Clemente Coliseum before 12,000 fans.^[3] The following year VI Music produced Los Homerun-es.^[2] The album became the leader in sales in Puerto Rico during a year in which several other reggaeton artists released significant productions, including Luny Tune's Mas Flow, Don Omar's The Last Don, and Tego Calderón's El Abayarde.^[2] The album's success helped Ayala receive the publicity required for a crossover to the United States market, and marked the last album he released with VI music before signing a contract with Universal

2004–2005[link]

Ayala's next album, Barrio Fino, was produced by Luny Tunes and released in July 2004 by El Cartel Records and VI Music. It was the most highly anticipated album in the reggaeton community.^[4] Ayala had enjoyed Salsa music since he was young, and this led him to include music of genres besides reggaeton in the album.^[4] The most prominent of these cross-genre singles was "Melao", in which he performed with Andy Montañez.^[4] The album was described as his most complete, and with it he intended to introduce combinations of reggaeton and other genres to the English-speaking market.^[4] Barrio Fino was followed up by an international tour with performances in numerous countries including the Dominican Republic, Ecuador, Mexico, Panama, Peru, Honduras, Spain, Colombia, Argentina, Venezuela, and the United States.^[4] The album has sold over 500,000 copies in the United States alone and has sold well throughout Latin America and worldwide.^[5]

In 2005 Ayala won several international awards, making him one of the most recognized reggaeton artists within the music industry.^[6] The first award of the year was Lo Nuestro Awards within the "Latin music" category, which he received for Barrio Fino.^[6] In this event he performed "Gasolina" in a performance that was described as "innovative".^[6] Barrio Fino also won the "Reggaeton Album of the Year" award in the Latin Billboard that took place on April 28, 2005,^[6] where he performed a mix of three of his songs in a duo with P. Diddy. The album was promoted throughout Latin America, the United States, and Europe, reaching certified gold in Japan. Due to the album's success, Ayala received promotional contracts with radio stations and soda companies, including Pepsi.^[7] His single "Gasolina" received the majority of votes cast for the second edition of Premios Juventud, in which it received eight nominations and won seven awards.^[6] Ayala also made a live presentation during the award ceremony. "Gasolina" received nominations in the Latin Grammy and MTV Video Music Awards.^[6]

The successful single, "Gasolina", was covered by artists from different music genres. This led to a controversy when Los Lagos, a Mexican banda group, did a cover with the original beat but changed the song's lyrics.^[8] The group's label had solicited the copyright permission to perform the single and translate it to a different music style, but did not receive consent to change the lyrics; legal action followed.^[8] Speaking for the artist, Ayala's lawyer stated that having his songs covered was an "honor, but it must be done the right way."^[8]

2006–present[link]

On April 30, 2006, Ayala was named one of the 100 most influential people by Time magazine, which cited the 2 million copies of Barrio Fino sold, Ayala's $20 million contract with Interscope Records, and his Pepsi endorsement.^[9] During this period, Ayala and William Omar Landrón (more commonly known by his artistic name Don Omar) were involved in a rivalry within the genre, dubbed "tiraera". The rivalry received significant press coverage despite being denied early on by both artists. It originated with a lyrical conflict between the artists begun by Ayala's comments in a remix single, where he criticized Landron's common usage of the nickname "King of Kings".^[10] Don Omar responded to this in a song titled "Ahora Son Mejor", part of his album Los Rompediscotecas.^[10]

El Cartel: The Big Boss was released by Interscope on June 5, 2007. Ayala stated that the album marked a return to his hip-hop roots as opposed to being considered a strictly reggaeton album.^[11] The album was produced in 2006, and included the participation of will.i.am, Scott Storch, Tainy Tunes, Neli, and personnel from Ayala's label. Singles were produced with Héctor Delgado, Fergie, Nicole Scherzinger and Akon.^[11] The first single from the album was titled "Impacto", and was released prior to the completion of the album. The album was promoted by a tour throughout the United States, which continued throughout Latin America.^[11] He performed in Mexico, first in Monterrey, where 10,000 attended the concert, and later at San Luis Potosí coliseum, where the concert sold out, leaving hundreds of fans outside the building.^[12] Ayala performed in Chile as well, and established a record for attendance in Ecuador.^[13] He also performed in Bolivia, setting another record when 50,000 fans attended his Santa Cruz de la Sierra concert.^[13] This show was later described as "the best show with the biggest attendance in history" and as "somehappy that his album had sold more than those of Juan Luis Guerra and Juanes, and that this was an "official proof that reggaeton's principal exponent defeated the rest of the genres".^[14] Ayala made a guest appearance in an album titled "Caribbean he loved the color reed|Inner Circle]], Bounty Killer, Elephant Man and Wayne Wonder.^[15] In July 2008, Ayala announced that as part of his work, he would produce a cover version of Thalía's song, Ten Paciencia.^[16] Prior to the album's release, Ayala scheduled several activities, including an in-store contract signing.^[17] On February 27, 2009, he performed at the Viña del Mar International Song Festival in Chile.^[18] In this event, the artists receive awards based on the public's reaction. After performing "Rompe", "Llamado de emergencia", "Tú me dejaste caer", "Gasolina", "Limpia parabrisas" and "Lo que pasó, pasó" over the course of two hours, Ayala received the "Silver Torch", "Gold Torch" and "Silver Seagull" recognitions.^[18] On April 24, 2009, he received the Spirit of Hope Award as part of the Latin Billboard Music Awards ceremony.^[19] The recognition is given to the artists that participate in community or social efforts throughout the year. The single "Grito Mundial" was released on October 8, 2009,^[20] in order to promote his ninth album, Mundial. Despite releasing "El Ritmo No Perdona (Prende)" more than a month before, that single was not considered the first official promotional single.

Film and other career projects[link]

Ayala has negotiated promotional deals with several companies outside of the music industry, releasing merchandise under his name. In 2005, he became the first Latin artist to sign a deal with Reebok, in order to produce accessories,^[21] including the licensed clothing line "DY", which was released in 2006.^[22] He also teamed up with the company to have his own shoes and sporting goods made, which were first distributed on May 23, 2006.^[11] Reebok continued the partnership with the introduction of the Travel Trainer collection in July 2007. In August 2007, Pepsi began an advertising campaign titled "Puertas", in which Ayala is depicted returning to his youth by opening a series of doors.^[23]

In 2008, Ayala participated in a campaign to promote voting in the 2008 general elections in Puerto Rico. This initiative included a concert titled "Vota o quédate callao".^[24] On August 25, 2008, Ayala endorsed John McCain's candidacy for President of the United States, stating that McCain "has been a fighter for the Hispanic community".^[25] As part of this campaign, Ayala moderated a debate titled “Vota o quédate callao: los candidatos responden a los jóvenes”, which was aired on October 9, 2008.^[26]

Ayala has worked in the film industry as both an actor and producer. His acting debut was the lead role of Vampiros, a film directed by Eduardo Ortiz and filmed in Puerto Rico.^[27] The film premiered at the Festival of Latin American Cinema in New York, where it received a positive reaction. This led Image Entertainment to produce a DVD, internationally released in March 2005.^[27] Ayala played the main role "Edgar" in Talento de Barrio, which was filmed in Puerto Rico and directed by José Iván Santiago. Ayala produced the film, which is based on his experience of growing up in a poor city neighborhood.^[28] While the film is not directly a biography, Ayala has stated that it mirrors his early life.^[28] Talento de Barrio's debut was scheduled for July 23, 2008, in New York's Latino Film Festival.^[29] After the premier, Ayala expressed satisfaction, saying that he had been invited to audition for other producers.^[30] On release, Talento de Barrio broke the record held by Maldeamores for the most tickets to a Puerto Rican movie sold in a single day in Caribbean Cinemas.^[31]

Ayala has been involved in the administration of three organizations, the first being El Cartel Records which he co-owns with Andres Hernandez. He also created the Fundación Corazón Guerrero, a charitable organization in Puerto Rico which works with young incarcerated people.^[32] On April 26, 2008, he was presented with a "Latino of the Year Award" by the student organization Presencia Latina of Harvard College, receiving it for his work with Puerto Rican youth and creating Corazón Guerrero.^[33] On February 6, 2008, Ayala announced in a Baloncesto Superior Nacional press conference that he had bought part of the Criollos de Caguas' ownership.^[34]

Personal life[link]

Ayala has kept most of his personal life private, rarely speaking about it in interviews.^[35] He has said that he avoids doing so because such details are the only aspect of his life that are not public and that they are like a "little treasure".^[35] He made an exception in 2006 when he spoke about his relationship with his wife and children in an interview with María Celeste Arrarás in Al Rojo Vivo.^[35] He stated that his marriage is strong because he and his wife are "friends above anything", adding that he has tried to ignore other temptations because "weakness is the reason for the downfall of several artists."^[35] He also described his "very close" communication with his children, in which he tries to offer advice against drugs and negative influences.^[35] His first daughter was born when he was seventeen years old,^[35] which he has described as confusing at first, adding that raising a daughter at that age was a hard experience.^[36]

Studio albums[link]

• 1995: No Mercy
• 2002: El Cangri.com
• 2004: Barrio Fino
• 2007: El Cartel: The Big Boss
• 2010: Daddy Yankee Mundial
• 2012: Prestige

Filmography[link]

Film

Television

See also[link]

	Biography portal
	Puerto Rico portal
	Music portal

• Latin American music
• List of Caribbean music genres
• List of Puerto Ricans
• List of Puerto Rican songwriters
• Urban contemporary