MODULE 9-12

PUPIL

Its size is controlled by the IRIS, thereby controlling the amount of light that enters the eye

LENS

focuses the image on the RETINA, from which the OPTIC NERVE conveys the visual message by electric impulse to the brain.

RETINA

Contains some 150 million light

CONE CELLS

These are responsible for the ability to discriminate detail such as: Sensation of color; and Detection of luminaires in the range of 3 – 1,000,000 cd per square meter

FOVEA

is an area of pinhead size containing about 100,000 cone cells which accounts for the extreme precision of foveal (center

HUMAN FACTORS

optical performance of the eye, color perception, and general condition of the eye

ENVIRONMENTAL FACTORS

relative brightness of the task and its surrounding, glare from the task, and movement involved in the specific task

LIGHTING UNITS

are psychophysical since they are a combination of human response and physical units of power

LUMINOUS INTENSITY SYMBOL

I

LUMINOUS FLUX UNIT

lumen (lm), in both SI and I P units

LUMINOUS FLUX

the total light emitted by a source or received by a surface , light quantity, a unit of power; can be expressed in watts, and it is the time rate of flow of perceived luminous energy
 

ILLUMINANCE Unit

lux (lx), SI unit [one lumen per square meter] footcandle (fc) I P unit

ILLUMINANCE

the luminous flux density at a point on a surface

LUMINANCE UNIT

candela per square meter

LUMINANCE

the intensity of the light emitted in a given direction per projected area of a luminous or reflecting surface; formerly photometric brightness

1 WATT

681 lumens

COEFFICIENT OF UTILIZATION (CU)

a coefficient made up of a number of factors such as room size, room shape, material reflectance, and luminaire distribution

VISUAL COMFORT

describes the subjective response of people to the glare of a lighting system

PHOTOMETRIC DISTRIBUTION CURVES

a two-dimensional representation or “map” of intensity (candelas) measure from

many different directions

ILLUMINANCE METERS

are used for field measurement of illuminance levels and these devices contain photoelectric material connected to a microammeter via electronic control circuitry and are calibrated in lux, footcandle or both

YELLOW GREEN

Maximum sensitivity at high illuminance levels is in the _ area (wavelength
of 555nm)

RED AND BLUE

Sensitivity at the _ ends of the spectrum is quite low.

COLOR CORRECTION

Correction of the cells (meters) for light incident at oblique angles that does not
reach the cell due to reflection from the surface glass and shielding the lightsensitive cell by the meter housing.

WORKING PLANE

Where no definite heights are specified, readings are taken at 75 cm (30 inches) above the floor

INVERSE SQUARE LAW

Illumination is inversely proportional to the square of the distance from the source.

LIGHT REFLECTANCE

the ratio of reflected to incident light; a measure of total light reflected, also called reflectance, reflectance factor, and reflectance coefficient, reflectance can be either specular or diffuse; or a combination of both
specular reflection

WORK SURFACES

20 to 40% and Light woods,
Medium and light laminates, Medium and light ink blotters
 

FLOORS

10 to 20% and Medium to light carpet,
Medium to light wood,
Medium tile

CEILINGS

70% or greater and White fabric / cloth ceiling, White mineral ceiling, Off white to white dry wall
 

OPEN OFFICE PARTITIONS

20 to 50% and Medium to light fabrics, Medium to light laminates

LIGHT TRANSMITTANCE

The luminous transmittance of a material is a measure of its capability to transmit incident light, The ratio of the total transmitted light to the total incident light. and, Also called transmittance, transmission factor, and coefficient of transmission

LUMINOUS INTENSITY UNIT

Candela (cd or cp), SI unit

LUMINOUS INTENSITY

the quantity which describes the power of a source or illuminated surface to emit light in a given direction , sometimes called candlepower, a characteristic of the source, and independent of the visual sense.

LUMINOUSFLUX SYMBOL

Φ