1. Announcement Filed trip is on Monday, May 6th from 8 to 9 AM
We will meet in front of NMS building
at 7:55 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. 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 from surface in the direction of view
– define the brightness of surface – important for contrast
r=1
1cd

12. Important quantities Chapter 14.2 (Tao and Janis)
Sections: , , , 1
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? Types: 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 Type Color Temp. (K) Efficacy (lumens/W) CRI
Lifetime
(1000 hours)
Mercury
5710
20-60
15-50 24
HPS
High pressure sodium
2100
140
22-70
16-40
LPS
Low pressure sodium
1740
(yellow)
200 ~0
10-201
Metal Halide
3600
~100
<70
10-20
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 Convert to effective reflectance (ρcc, ρw, ρfc)
White ceiling, Rc = 70 – 80 % = ρc
White walls, Rw = % = ρw
Medium to light colored walls, Rw = 50 % =ρw
Dark wood paneling, Rw = 25 % = ρw
Floor, Rf = % = 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 , ρ w, 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