Definition: The radiant (luminous) intensity is the power per unit solid angle from a point. CS348B Lecture 5 Pat Hanrahan, Spring 2000

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1 Radant and Lumnous Intensty Defnton: The adant (lumnous) ntensty s the powe pe unt sold angle fom a pont. dφ I(ω) Φ S I( ω) W candela cd s lm s The Inventon of Photomety Bougue s Classc expement Compae two lght souces One s a candle Defnton of a standad candle Ognally standad candle Cuently 550 nm lase wth /683 W/s Page

2 Lumnance of Common Souces Sky Suface of the sun,000,000,000. cd/m Sunlght clouds 30,000. Clea day 3,000. Ovecast day 300. Moonlght 0.03 Moonless Lght Souces Popetes Spectal Blackbody (ncandescent) Flouescent Pont o aea Dectonal dstbuton gonometc dagam Page

Wan s Spotlght I( ω) cos s Φ π 0 I( ω ) d cos dϕ π s cos d cos π s 0 0 + s + I ( ω) Φ cos π s Gonometc

3 Wan s Spotlght I( ω) cos s Φ π 0 I( ω ) d cos dϕ π s cos d cos π s s + I ( ω) Φ cos π s Gonometc Dagams Isocandle dagam fo Novalux sodum lumnae Fom Pay Moon The Scentfc Basc of Illumnatng Engneeng p. 36 Page 3

4 Iadance and Illumnance Defnton: The adance (llumnance) s the powe pe unt aea ncdent on a suface. de( x) L( ω ) cos L( ω ) E( x) W m H L( ω )cos lm Lux m Ths s sometmes efeed to as the adant and lumnous ncdence. Iadance Dstbuton Isolux contous Page 4

5 Isotopc Pont Souces h I( ω) Φ 4π 3 Φ cos Φ cos dφ E da I da 4π 4π h Note nvese squae law fall off. Note cosne dependency da Dstant Souce E s s E E s cos s Page 5

6 Hemsphee: Poected Sold Angle cos π? Dsk R E cosd π 0 cos πl Lπ sn Lπ Lcos dφ d cos d + R cosd Page 6

7 Sphee R E Lcos Lπ sn Lπ R The Sun Sola constant (nomal ncdence at zenth) Iadance 353 W/m Illumnance 7,500 Lumen/m 7.5 Klo-Lux Sola angle a.5 degees.004 adans (half angle) w p sn a 6 x 0-5 steadans Radance 3 E W / m 7 W L ω 6 0 s m s Pluto (6 tea-metes) 50 Lux - ead a newspape Deep space -> 0 mco-lux (see, but not ead!) Page 7

8 Polygonal Souce Lambet s Fomula N γ 3 A A A A γ N N n A n γ A 3 N N Page 8

9 Fom Facto x cos d ω da x x da T x x A A cos cos π x cos x da da cos cos d ω da x x Fom Factos Dffeental-dffeental Dffeental-fnte Fnte-fnte F da, da cos ocos F d da, A A A π x x cos ocos FA da da, A A A A π x x cosocos π x x da Page 9

10 Fom Facto Popetes Fom facto s the pecentage of lght tansfeed between sufaces. Recpocty T o A F A A cos cos π x x da da T A F. Summaton F F Radosty and Lumnosty Defnton: The adosty (lumnosty) s the enegy pe unt aea leavng a suface. L( ω ) o B( x) H L( ω o )cos o o o W m Lux lm m Ths s offcally efeed to as the adant and lumnous extance. Page 0

11 Unfom Dffuse Souce B L Lcos πl cos L B π 3 blondel apostlb nt cd / m ( skot 0 apostlb ) π π lambets cd /cm foot lambets π 3 cd / ft ( glm 0 foot lambet ) π Radometc and Photometc Tems Physcs Radomety Photomety Enegy Radant Enegy Lumnous Enegy Flux (Powe) Radant Powe Lumnous Powe Flux Densty Iadance Radosty Illumnance Lumnosty Angula Flux Densty Radance Lumnance Intensty Radant Intensty Lumnous Intensty Page

12 Photometc Unts Photomety Unts MKS CGS Btsh Lumnous Enegy Lumnous Powe Illumnance Lumnosty Talbot Lumen Lux Phot Footcandle Lumnance Nt Stlb Apostlb, BlondelLambet Footlambet Lumnous Intensty Candela (Candle, Candlepowe, Cacel, Hefne) Thus one nt s one lux pe steadan s one candela pe squae mete s one lumen pe squae mete pe steadan. Got t? Kaya Page

Rays. CS348B Lecture 4 Pat Hanrahan, 2004

Rays. CS348B Lecture 4 Pat Hanrahan, 2004 Page 1 Light Visible electomagnetic adiation Powe spectum 1 10 10 4 10 6 10 8 10 10 10 1 10 14 10 16 10 18 10 0 10 10 4 10 6 Powe Heat Radio Ulta- X-Rays Gamma Cosmic Infa- Red Violet Rays Rays 10 16 10