1. Module 2 Lighting Fundamentals

2. Purpose of the Module
To describe the relationship of light and color and the different source color characteristics
To discuss the basic principles involved in lighting and how they meet the physiological and psychological needs and responses of the people to the luminous environment.
To enumerate the 5 lighting metrics, namely, luminous flux, illuminance, luminous intensity, luminance and luminous exitance.
To present important technical terms and terminologies used in the lighting system.

3. Outline Light and Color Light, Vision and Perception Lighting Metrics
Use of Light
Direction of Light
Source Color Characteristics
Quantity
Light, Vision and Perception
Lighting Metrics
Terminologies

4. Light and Color
Light is defined as “visually evaluated radiant energy”
Light is a form of energy, transmitted by radiation, and that it is energy to which the human eye is sensitive.
Newton (1600s): All heated bodies emit energetic corpuscles, each having the same very high velocity and a size dependent upon its color; postulated to travel in straight lines and could be reflected and refracted.
Huygens (1670): Every point on an advancing wavefront serves as a source of secondary wavelets, sent out radially
Maxwell & Hertz (19th century): Showed that all radiant energy consists of electromagnetic waves travelling at the velocity of light.

5. Light and Color Best natural source of light is the sun
The visible portion of the electromagnetic spectrum includes all wavelengths between 380 nm and 770 nm
Incandescent – tend to produce light with greater amounts of power in the longer wavelength ends of the spectrum (reds & oranges); accounts for warm appearance

6. Light and Color Ability To See Color
Subtractive primaries – basis for the development of all manufactured paints and dyes
Additive primaries – what the eye uses in the process of seeing light and color

7. Use of Light
Accessibility to electric light is almost taken for granted, even in the most remote locations
Challenge is not only to provide light in an energy efficient manner but to provide also a high quality of light.
Factors that can be controlled in the design of a lighting system
Direction
Color
Brightness (luminance)
Quantity (illuminance)

8. Direction
Directionality of the lighting can enhance and emphasize an object’s perceived shape or form
Techniques used:
Key
Fill
Grazing
Wall washing
Silhouette
Uplight
Others

9. Direction Key Light Fill Lighting Single point source of light
Provides highlights and casts shadows providing contrast and producing definite focus
Fill Lighting
Multi-directional or diffuse light
Reduces shadows on an object caused by the key light
If totally diffuse, creates a cloudy day feeling and minimizes shadows, which may be desirable for certain tasks

10. Direction Grazing Wall Washing
Occurs when light strikes a surface at a sharp angle, nearly parallel to a rough surface
Enhances any variations in surface depth, revealing texture
Will also emphasize flaws and unevenness in surfaces
Wall Washing
Occurs when light strikes a surface at a wide angle
Provides even lighting on a vertical space, increase luminance of wall surfaces, and extend the space.
Grazing
Wall Washing

11. Direction Silhouette Uplight
Light source is used not to illuminate an object itself, but its background
Applicable when one aims to reveal the outline of an object against a brighter surface and to create separation between the object and its background
Uplight
Places a light source below an object
Produces shadows that are reversed from how an object is shadowed in daylight
Creates an eerie, unnatural effect because it replaces the more familiar overhead orientation of the light source.

12. Ideal Direction of the Lighting
Should be determined by the space function or tasks
Shadows at a work task may be irritating
Excessive concentration and constant readaptation of the eye can cause visual fatigue and a loss in performance or increase in accidents
Highlights and shadows must be used sparingly depending on the task to prevent the introduction of negative factors
Highlights and shadows, on the other hand, provides a pleasant visual environment located away from the major tasks

13. Source Color Characteristics
Color is defined with a variety of metrics but the 2 most common are:
Correlated Color Temperature (CCT)
Color Rendering Index (CRI)

14. Correlated Color Temperature (CCT)
Represents the relative whiteness of a light source, whether the source appears warm, cool or neutral
Measured in Kelvin (K)
Acceptable range of CCTs for indoor environments is between 2500K and 5000K, with the higher value representing a cooler source
Often the first criterion considered in the development of a space’s image

15. Correlated Color Temperature (CCT)
CCT of a lamp refers to the absolute temperature of a blackbody when its visible radiation most closely matches the color of the lamp.
Major mood-setting element of the space
Warm color helps to create an intimate or cozy space
Cool color associated with a business like environment

16. Color Rendering Index (CRI)
CRI rating indicates how well an object’s colors are rendered by a source.
It is a comparison of 8 specific test colors under an ideal light source in question.
When color rendering is important, a source with a high CRI (e.g. 3500K fluorescent with a CRI of 85) should be selected
If not important, a CRI in the mid 70s is less expensive and may meet the client’s needs
If extremely important, a CRI in the 90s may be recommended

17. Quantity (Illuminance)
Quantity of light is commonly described in illuminance levels because these are easy to measure
In order to effect a noticeable increase in light level, the illuminance must be increased by a factor of about 2 to 1
Glare – result of excessive, uncontrolled light within the field of view
The principal determinants are intensity, size of background brightness, and position in the field of view of the light sources
Luminance ratios of 5 to 1, 10 to 1, and 20 to 1 are often used to provide highlights or for accent lighting

18. Light, Vision and Perception
Light interacts with surfaces and objects in space and with the human visual system, affecting our perception of visual tasks
Visual perception requires
a light source, the stimulus
a modifier of the light source
a receiver, the eye
a decoder, the brain to analyze the modifier

19. The Eye and Vision
Cornea – transparent membrane that bends the light rays as they enter the eye
Light rays travel through an opening in the iris called the pupil; the size of the pupil controls the amount of light that enters the back part of the eye
The light passes next through the lens
The ciliary muscle changes the thickness of lens to bring image of the object in retina
The retina is the innermost layer of the eye and contains the light sensitive cells

20. Lighting Metrics Luminous Flux Illuminance Luminous Intensity
Luminous Efficacy and Efficiency

21. Luminous Flux Defined as the flow of light,  Measured in lumens
Power
Luminous Flux
Defined as the flow of light, 
Measured in lumens
A lamp receives watts and emits lumens. The measure of success of doing this is called efficacy and is measured in lumens per watt (lm/W)

22. Lamp Efficacies 100-W incandescent 1750 18 100-W tungsten halogen 1880
LUMENS
LUMENS/WATT
100-W incandescent
1750 18
100-W tungsten halogen
1880 19
13-W compact fluorescent
900 69
32-W fluorescent
2950 92
175-W metal halide
14000 80
150-W high pressure sodium
16000
107
Source: IESNA Lighting Education: Fundamental Level

23. Average illumination of a surface is luminous flux
Illuminance
As luminous flux travels outward from a source, it ultimately impinges on surfaces, where it is reflected, transmitted, and/or absorbed
Illuminance on a surface, E is the density of luminous flux incident on that surface
Measured in lumens per square meter
Lumen/m2 is called a lux while lumen/ft2 is called footcandle
ILLUMINANCE
Average illumination of a surface is luminous flux
per unit area.

24. Typical Illuminance Levels
VISUAL ACTIVITES
RECOMMENDED LEVEL IN LUX
RECOMMENDED LEVEL IN FOOTCANDLE
Lighting for safety
5-20
0.5-2
Lobbies
100 10
Stairways 50 5
Reading #2 pencil
300 30
Reading #3 pencil
500
Inspection (Simple-Difficult)
30-500
Handcrafts
30-100
Fine Machine Work
3000
Source: IESNA Lighting Education: Fundamental Level

25. Luminous Intensity
Generally speaking, a light source emits its luminous flux (Φ) in different directions and at different intensities. The visible radiant intensity in a particular direction is called luminous intensity (I). The unit of measurement is the candela (cd).

26. Luminance
The luminance (L) is the brightness of an illuminated or luminous surface as perceived by the human eye. Unit of measurement is candelas per square meter (cd/m2).

27. Luminous Efficacy and Efficiency
Luminous Efficacy (η). Luminous efficacy indicates the efficiency with which the electrical power consumed is converted into light. The unit of measurement is lumens per watt (lm/W).
Luminaire Efficiency. Luminaire efficiency (also known as the light output ratio) is an important criterion in gauging the energy efficiency of a luminaire. This is the ratio between the luminous flux emitted by the luminaire and the luminous flux of the lamp (or lamps) installed in the luminaire.

28. Laws for Point Sources of Light
The following are used to calculate the illuminance at a single point in a plane
Inverse Square Law
Cosine Law of Incidence

29. Inverse Square Law
To understand this law, consider a cone-shaped beam of light coming from a small point source and hitting a surface some distance away. Suppose that the luminous flux within the cone is one lumen, and that it strikes a surface 1-meter away, producing an illuminated area of 1 square meter. By dividing the luminous flux by the area we can find the illuminance, which will be 1 lux.
The illuminance E equals the intensity of the light source (I), divided by the distance squared (d2 ).

30. Cosine Law of Incidence
If the surface is turned so that the rays hit it at an angle, the illuminated area will increase in size and the illuminance will drop accordingly. The ratio of the original illuminated area to the new area is equal to the cosine of the angle through which the surface has been moved. Therefore the illuminance will fall by the factor of the cosine of angle. This is where Lamberts Second Law comes in, the Cosine Law of illuminance.
If a surface is illuminated to 100 lux and is twisted through an angle of 60 degrees then the illuminance will fall to half or 50 lux, because the cosine of 60 degrees is ½.

31. The Effect upon the Illuminance when
hitting a Different-Angled Surface

32. Lighting Terminologies and Basic Units
Quantity
Quantity is a
Measure of
Symbol
Unit in SI
Definition of Unit
Luminous Intensity (Candlepower)
Ability of source to produce light in a given direction I
Candela (cd)
Approximately equal to the luminous intensity produced by a standard candle
Luminous Flux
Total amount of light Ø
Lumen (lm)
Luminous flux emitted in a solid angle of 1 steradian by a 1 candela uniform point source
Illuminance (illumination)
Amount of light received on a unit area of surface (density) E
Lux (lx)
One lumen equally distributed over one unit area of surface
Luminous exitance
Density of light reflected or transmitted from a surface M
Lm/m2
A surface reflecting or emitting 1 lumen per unit area
Luminance (brightness)
Intensity of light per unit area reflected or transmitted from a surface L
Cd/m2
A surface reflecting or emitting light at the rate of 1 candela per unit of project area
1 meter (m) = 3.28 ft; 1 cd/m2 = 3.14 lm/m2
1 m2 = (3.28 ft)2 = ft2; 1 cd/in2 = 452 lm/ft2; 1fc = lux

33. Lamp Families and Some Common Lamps Types
* Although shown in this figure, these lamps are not considered
efficient energy-saving lamps