module 2v - light & lighting fundamentals

8/12/2019 Module 2V - Light & Lighting Fundamentals

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Module Light and Lighting

Fundamentals

Philippine Efficient Lighting Market

Transformation Project (PELMATP)

Module 2

Light and Lighting Fundamentals

(3 hours)


Fundamentals



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 andhow 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.


Fundamentals



Outline

Light and Color

Light and Color

Use of Light

Direction of Light

Source Color Characteristics

Quantity

Light, Vision and Perception

Lighting Metrics

Terminologies


Fundamentals



Light and Color

Light is defined as visually evaluated radiant energy

Light is a form of energy, transmitted by radiation, andthat it is energy to which the human eye is sensitive.

Newton (1600s): All heated bodies emit energeticcorpuscles, each having the same very high velocity anda size dependent upon its color; postulated to travel instraight lines and could be reflected and refracted.

Huygens (1670): Every point on an advancing wavefrontserves as a source of secondary wavelets, sent outradially

Maxwell & Hertz (19th century): Showed that all radiantenergy consists of electromagnetic waves travelling atthe velocity of light.


Fundamentals



Best natural source of light is the sun

The visible portion of the electromagnetic spectrumincludes all wavelengths between 380 nm and 770 nm

Incandescent tend to produce light with greater amountsof power in the longer wavelength ends of the spectrum(reds & oranges); accounts for warm appearance

Light and Color


Fundamentals



Light and Color

Ability To See Color

Subtractive primaries

basis for the

development of all

manufactured paintsand dyes

Additive primaries

what the eye uses in

the process of seeing

light and color


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Fundamentals



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 energyefficient 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)


Fundamentals



Direction

Directionality of the lightingDirectionality of the lighting can enhance and

emphasize an objects perceived shape or form

Techniques used:Key

Fill

Grazing

Wall washing

Silhouette

Uplight

Others


Fundamentals



Direction

Key Light

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


Fundamentals



Direction

Grazing

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 luminances of wall surfaces, and extend

the space.

Grazing

Wall

Washing


Fundamentals



Direction

Silhoutte

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.


Fundamentals



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 accidentsHighlights 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


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Fundamentals



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)


Fundamentals




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 2500K and 5000K,

with the higher value

representing a cooler source

Often the first criterion

considered in the development

of a spaces image


Fundamentals




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


Fundamentals



Color Rendering Index (CRI)

CRI rating indicates how well an objects colors arerendered by a source.

It is a comparison of 8 specific test colors under an ideallight source in question.

When color rendering is important, a source with a highCRI (e.g. 3500K fluorescent with a CRI of 85) should beselected

If not important, a CRI in the mid 70s is less expensiveand may meet the clients needs

If extremely important, a CRI in the 90s may berecommended


Fundamentals



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 thefield 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


Fundamentals



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 perceptionrequires

a light source, the

stimulus

a modifier of the light

source

a receiver, the eye

a decoder, the brain to

analyze the modifier


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Fundamentals



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 backpart 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


Fundamentals



Lighting Metrics

Luminous Flux

IlluminanceLuminous Intensity

Luminance

Luminous Exitance


Fundamentals



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)

Power

Luminous

Flux


Fundamentals



Lamp Efficacies

10716000150-W high pressure sodium

8014000175-W metal halide

92295032-W fluorescent

6990013-W compact fluorescent

191880100-W tungsten halogen

181750100-W incandescent

LUMENS/WATTLUMENSLAMP

Source: IESNA Lighting Education: Fundamental Level


Fundamentals



Illuminance

As luminous flux travelsoutward from a source, itultimately impinges on surfaces,where it is reflected,transmitted, and/or absorbed

Illuminance on a surface, E isthe density of luminous fluxincident on that surface

Measured in lumens per squaremeter

Lumen/m2 is called a lux whilelumen/ft2 is called footcandle

ILLUMINANCE

Average illuminationof a surface is

luminous flux per

unit area.


Fundamentals



Typical Illuminance Levels

3003000Fine Machine Work

30-100300-1000Handcrafts

30-500300-5000Inspection (Simple-Difficult)

50500Reading #3 pencil

30300Reading #2 pencil550Stairways

10100Lobbies

0.5-25-20Lighting for safety

RECOMMENDED

LEVEL IN

FOOTCANDLE

RECOMMENDED

LEVEL IN LUXVISUAL ACTIVITES

Source: IESNA Lighting Education: Fundamental Level


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Fundamentals



Luminous Intensity

Generally speaking, a light source emits its luminous flux

() in different directions and at different intensities. The

visible radiant intensity in a particular direction is calledluminous intensity (I). The unit of measurement is the

candela (cd).


Fundamentals



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

).


Fundamentals



Luminous Efficacy and Efficiency

Luminous Efficacy (). 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.


Fundamentals



The following are used to calculate the

illuminance at a single point in a plane

Inverse Square Law

Cosine Law of Incidence

Laws for Point Sources of Light


Fundamentals



Inverse Square Law

To understand this law, consider a cone-shaped beam of lightcoming from a small point source and hitting a surface somedistance away. Suppose that the luminous flux within the cone isone lumen, and that it strikes a surface 1-meter away, producing anilluminated area of 1 square meter. By dividing the luminous flux bythe area we can find the illuminance, which will be 1 lux.

The illuminance E

equals I, the

intensity of the

light source,

divided by the

distance squared.


Fundamentals



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 theilluminance will drop accordingly. The ratio of the originalilluminated area to the new area is equal to the cosine ofthe angle through which the surface has been moved.

Therefore the illuminance will fall by the factor of thecosine of angle. This is where Lamberts Second Lawcomes in, the COSINE LAW of illuminance.

If a surface is illuminated to 100 lux and is twistedthrough an angle of 60 degrees then the illuminance willfall to half or 50 lux, because the cosine of 60 degrees is.


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Fundamentals




Fundamentals




Fundamentals



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