Lighting - The Basics

Measuring Light

Light is measured in lumens and lux.

The 'lumen' is the unit of flow of light, from any one source.

This table shows how much light different light sources give:

one candle

12 lumens

one gas mantle

600-700 lumens

one 100 watt electric bulb

1200 lumens

Thus ten candles give about the same light as a 10 watt bulb and a gas mantle is equivalent to a 50 watt bulb.

The 'lux' measures the amount of light striking a surface. One lux is one lumen per square metre. In the USA, the term 'foot-candle' i.e. lumens per square foot, is used.

For example:

fitting type range lux  

one low-voltage halogen spotlight with a 35-watt bulb or 100-watt spotlight bulb

3 metres

500

from ceiling to floor

as above

1.5-2 metres

1000

from ceiling to table or desk

A safe minimum for a room is 50 lux.

Glossary

bowl

a ceiling-mounted, upward pointing light with a glass bowl underneath

bracket

wall-light, often swivelling

candelabrum

a branched candlestick or lamp with several lights

candle stick

traditional fitting holding one or more candles

chandelier

pendant from ceiling with three or more arms, lit using candles, and usually decorated with glass crystal decorations

electrolier

an electric chandelier

gasolier

a gas-lit chandelier

lantern

a glass-enclosed light, in house lighting generally hung from the ceiling

pendant

a hanging light with less than three light sources, or otherwise used as a generic name for any hanging light

picture light

a wall-mounted light used in an accent role to illuminate a picture

sconce

a wall-light employing a candle, with an ornamental bracket

uplighter

upward pointing light, usually wall-mounted