ILLUMINATION

lights

it is a form of radiant energy from natural resources that travels in the form of an electromagnetic wave so it has a wavelength and a known speed.

lighting

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

cornea

the transparent membrane that bulges out at the front of the eye

iris

is a thin circular structure in the eye responsible for controlling the diameter and size of the pupil and the amount reaching the retina

pupil

is a hole locatedin the center of the iris that allows light to enter the eye.

lens

a transparent biconvex structure in the eye that helps to refrack light to be focused in the retina

retina

is a light sensitive layer of tissue, lining the inner surface of the eye

optic nerve

transmits visual information from the retina to the brain for processing.

parts of eye

• cornea

• iris

• pup

two types of receptors

• rods

• cones

adaptation

ability of the eye to adjust to higher or lower levels of luminance

photopic (daytime)

the cones operate during the day and nominal daylight enables us t see in detailed color

mesopic

is the light conditions are not bright as the rods can see a black and white image, the overall impression is much less brightly color

scotopic (nighttime)

at lower levels much lower than the average street lighting or moonlight the cones cease to function.

types of adaptation

• photopic

• mesopic

• scotopic

luminous flux

all the radiated power emitted by a light source and perceived by the eye

luminous flux unit

lumens (lm)

luminous intensity (I)

is the measure of light output in a specified direction

unit of luminous intensity (I)

candela (cd)

illuminance (E)

is the measure of the amount of light falling on a surface

illuminance units

lux = lumens/m²

two factors affecting the light efficiency

• quantity of light

• quality of light

quantity of light

is the needed for any visual object is based on the size of the object details, the contrast between the details in their background and the time allowed for the viewing objects.

quality of light

it pertains to the distribution of brightness in the lighting installation.

quality of light includes several elements

• color

• psychological effect

• aesthetics

• economics

factors that affect illumination

• brightness

• contrast

• glare

• diffuseness

types of modern artificial light sources

• incandescent filament lamps

• electric discharge lamps

correlated color temperature (CCT)

refers to the whiteness of the light that a source emits

low CCT

more yellow and red (warm)

high CCT

more bluish white

neutral CCT

around 3500 K

color rendering index (CRI)

is a light source that measures the degree of color shift which objects when illuminated by the light source.