Announcement Filed trip is on Monday, May 6 th from 8 to 9 AM

1. We will meet in front of NMS building at 7:55 AM AnnouncementFiled trip is on Monday, May 6thfrom 8 to 9 AM

2. Objectives • Define lighting quantities and systems • Learn about lighting design

5. Vision and light • Brightness, pattern, motion, and color • Which is more sensitive – eye or camera? • Which is more important, brightness or contrast?

6. Color • Does color change the apparent size of rooms? • Does color change perception of temperature, noise, elapsed time?

7. Want is light ? • Light – electromagnetic radiation • Radiation wavelength • Visible light 0.4 – 0.7 μm

8. Solar radiation spectrum Major part of solar radiation is visible light

9. Photometrics • Luminous intensity [candela, cd] • Define the ability of light source to generate light (illumination) in given direction • Power – luminous flux [lumen, lm] • Quantity of light • Illuminance – light power density [foot-candela, fc] [lux, lx] SI units • Density of light (illumination) incident on a surface • Luminance - surface brightness [foot-lambert, lm/ft2] • directional emission of visible light

10. Relation between: 1) Luminous intensity [cd] and 2) Illuminance [fc] fc = cd / distance2

11. r=1 1cd Units and conversion • 1 cd = Area of unit sphere = 4·π = 12.57 lumens Luminous flux [lumen]= Luminous intensity [cd] ·(4·π) • Illuminance [foot-candle, lux] = Luminous flux [lumen]/Area [ft2,m2] • Luminance [Foot-lambert] = lumen/ft2 fromsurface in the direction of view – define the brightness of surface – important for contrast

12. 1 Important quantities Chapter 14.2 (Tao and Janis) • Sections: 14.2.3, 14.2.4, 14.2.5, 14.2.6 Ref: Tao and Janis (2001)

13. Major design parameters • Lighting systems (lamps): • Define Luminous flux [lumen] • Required level of light at design spot (table spot on the wall etc.) • Defined by Illuminance level (E)

14. Color of light • Color temperature is used to express the color of the light

15. Surface color rendering Depending on the light type the surface colors can be different Depends on spectral energy distribution

16. Terms for Lamps • What is luminous efficacy? • What does a lifetime of 1000 hours mean? • What affects lifetime? • Does color rendering index (CRI) indicate if a lamp source will cause a color shift?

17. Luminous efficacy • Define the light output per unit of electric power input Efficacy = Lumens/Watt

18. Incandescent • Thomas Edison first incandescent lamp • Efficacy of 1.4 lumens/watt • Life – 750 to 1000 hours • 10 – 20 % decay in output

20. Is Dimming Bad For Incandescent Lamps? - 10% lower Voltage - 25% lower light - life of lam double

21. Fluorescent Lamps • Electrodes arc through mercury vapor • Phosphors fluoresce in visible range • Efficacy of 60 to 100 lumens/watt (after burn-in)

22. Fluorescent Lamps • Electrodes arc through mercury vapor • Phosphors fluoresce in visible range • Efficacy of 60 to 100 lumens/watt (after burn-in)

23. Ref: Tao and Janis (2001)

24. Fluorescent Lamps • 20,000 hour life for tubes • Output falls off significantly (lumen deprecation) • We define mean lumens at 40% expected life • Environmental hazard because of mercury • Significant improvement with lumen deprecation and life with new types of fluorescent lamps • Start of the lamp vary with type of fluorescent lamp

25. Ballasts • Why do we need ballasts? • Transformer –higher voltage • Limit the maximum flow of current - choke • Types: • Magnetic • Noisier, cheaper, less efficient (more heat) • Electronic • Quieter, better power factor, more expensive • Lower harmonic distortion • Higher frequency

26. High Intensity Discharge (HID) • Arc through conducting vapor • High temperature and pressure • Ceramic or quartz tubes • Glass protective casing • Also need ballast (electric discharge lamps)

27. Ref: Tao and Janis (2001)

28. Types of HID Lighting 1minimal decline in output with aging

29. Issues with HID lighting • Long start-up ~ minutes • Arc needs to stabilize, heat vapor • Even longer restart • Up to 40,000 hour life time

30. LED • Replacing all technologies • …..

31. Illumination Calculation • E = N × F × LLF × LOF × CU / A • E = selected illuminance [fc, lx] • N = number of fixtures • F = installed lumens per fixture [lm] • LLF = Light loss factor • depreciation, position (dust deposit) • LOF = lamp operating factor • Ballast, voltage • CU = coefficient of utilization • Fraction of light that meets the work surface • A = room area [ft2, m2]

32. Zonal Cavity Method • Purpose is to get CU “fixture efficiency” • What parameters do you need?

33. Figure 16-1 Ref: Tao and Janis (2001)

34. Calculate Cavity Ratios • CR = 2.5 × PAR × h • PAR = perimeter to area ratio = P/A • PAR = 2 × (L+ W)/(L × W) • h = height of cavity • What about CR for non-rectangular rooms? • CR = 5 × (L+ W)/(L × W)× h

35. Reflectance • Experience • White ceiling, Rc = 70 – 80 % = ρc • White walls, Rw = 60 - 70 % = ρw • Medium to light colored walls, Rw = 50 % =ρw • Dark wood paneling, Rw = 25 % = ρw • Floor, Rf = 10-30 % = ρf • Convert to effective reflectance (ρcc, ρw, ρfc) • Tables in Tao and Janis (Table 16-6) or from manufacturer

36. Calculation Procedure • Goal is to get CU (how much light from the fixture gets to the work surface) • Data collection • Room geometry • Surface reflectance • Fixture tables • Preliminary calculations • CR for room, floor, and ceiling

37. Calculations (continued) • Table 16.6 • ρcc and ρfc (assume ρfc = 20% if no other information given) • Table 16.7 • CU Correction if ρfc ≠ 20% • Fixture table (Figure 16-6, or manufacturer) • CU based on ρcc , ρw,RCR • Use CU by multiplier from step 4.

38. Example • Classroom (30 × 30 × 9) • White ceiling, Medium colored walls, Light floor • Students working on desks • Fluorescent fixtures at ceiling level • Use standard tables