Light And Lighting Flashcards
Define illuminance
The amount of luminous flux per unit area.
Aka quantity of light on a certain surface
Define luminance
The intensity of light emitted from a surface per unit area into your eye
Define luminous flux
The measure of brightness of a light source in terms of energy being emitted
Measuring daylight factor
The percentage of lux inside the building compared to what is available outside for a standard overcast sky
Uniform standard sky for Britain
5000 lux for heavily overcast sky
CIE standard sky
The luminance steadily increases above the horizon
Define sky component
The light received directly from the sky
Define externally reflected component
The light received directly by reflection from buildings and landscape outside the room
Define internally reflected component
The light received from surfaces inside the room
What device measures light?
Light meter/ photometer
The Waldram diagram
A specially scaled grid representing half the hemisphere of sky
PSALI
Permanent supplementary artificial lighting of interiors
Lighting design to provide illuminations that appears to be of good daylight character
Incandescent lamps
Produce light by heating substances to a temperature
Discharge lamps
Produce light by passing an electric current through a gas or vapour
Luminous efficacy
The ability of a lamp to convert electrical energy to light energy end is measured by the ratio of light output to energy input
Colour temperature
1700 k orange low pressure sodium lamps
15,000 k-27,000k clear blue poleward sky
Correlated colour temperature
The absolute temperature of a perfect radiator when the colour appearance of the radiator best matches that of the light source
Colour rendering
The ability of a light source to reveal the colour appearance of surfaces
Colour rendering index
A number that indicated the accuracy by which a lamp shows surface colours
Tungsten filament lamps
Passing an electric current through a filament of metal and raising the temperature to white heat
Define luminaire
The light fitting that hold or contains a lamp
British zonal system
BZ system classifies luminaries into 10 classes. BZ1 downwards light, BZ10 upwards light
Utilisation factor
The ratio of the total flux reaching the working plane compared to the total flux output of the lamps
Glare
The discomfort or impairment of vision caused by an excessive range of brightness
Glare rating
An index or numerical measure of discomfort glare which enables glare to be assessed and acceptable limits recommended
Albedo
The measure of natural light from exterior surfaces into interior spaces
Pros and cons of daylight
Pros Good colour rendering Improve mood Influence sleep patterns Reduce need for artificial lighting
Cons Lack of control Glare Black hole effect Heat loss
Order from best to worst energy consumption of lamps
- Low pressure sodium lamps
- High pressure sodium lamps
- Mercury iodide lamp
- High pressure mercury vapour lamp
