Illumination

lumen

unit of luminous flux

area description

involves physical characteristics such as room dimensions, room reflectance and work location

light loss factor

ratio of illuminance when it reaches the lower level to the initial level

Light

form of radiant energy from natural and artificial sources

Light

like other electromagnetic radiation, it can be reflected and refracted

lighting

is the application of light to illuminate objects, surfaces, scenes, pictures and people

Luminous flux

is the light output of a light source

Luminous/Light Intensity

the visible radiant intensity in a particular direction

is the measure of light output in a specified direction

candela

unit of luminous/light intensity

Illuminance (E)

a measure of the amount of light falling on a surface

lux (lx)

unit of illuminance

Illumination

average illumination of a surface in luminous flux per unit area

Lux= lumens/m^2

unit of illumination

Luminous efficacy

indicates efficiency of the light source with which the electrical power consumed is converted into light

lumens per watt (lm/W)

unit of luminous efficacy

art, science

the design for indoor lighting system general illumination is considered to be more of an ______ than a __________ and it involves many variable factors

size and shapes of the space
types of finishes on ceilings, wall, and floors
details of the construction
economic consideration of costing
compatibility of the lighting system with the architectural design
type of activities in the area

factor of indoor lighting

determination of required level of illumination
quality required
quantity required
area atmosphere
area description and use
selection of system luminaire

objectives and design consideration

Illuminating Engineering Society of North America

IESNA

quality of light

distribution of brightness in the lighting installation

quantity of light

adequate level of illumination for the average person under normal condition

area atmosphere

analyze the environment in which the lighting system will operate

selection of system luminaire

depends upon the requirements and conditions stated

determining average illuminance

can be determined when a given number of luminaires used in a space is known

Work plane

is measured at the heigh of the visual task

0.75 meter

general height of work plane above the floor

work plane illuminance, Ewp

average maintained luminous flux that hits the work plane per unit area, unit is lx

total system lamp lumen output

the quantity of light produced by all lamps that are lighting a space

coefficient of utilization

ratio of the lumens that reaches the work plane to the total lumens given off by the lighting system

total light loss (maintenance factor)

product of all the individual factors that contribute to the loss of light

lamp lumen depreciation factor (LLD)

depreciation of lumen output of lamp through life

lamp dirt depreciation factor (LDD)

with the passage of time, dirt accumulates on lamps resulting to loss of light

room surface dirt depreciation factor (RSDD)

with the passage of time, the accumulation of dirt on the surface of the room further reduces the amount of light that reaches the work plane

lumen method

this method is used to design general overall lighting of the room, this calculates the illuminance that represents the average of the values at all points over the entire work plane of the room