Luminous flux
According to BRE’s The essential guide to retail lighting: The term 'luminous flux' describes the ‘amount of light produced by a lamp; usually measured in lumens’. Lumen are related to lux (lx), the SI unit of illuminance, or amount of light on a surface, in that one lux is equal to one lumen per square metre (lm/sq. m)
The Illustrated Guide to Electrical Building Services, Third Edition (BG 31/2017), by David Bleicher & Peter Tse, published by BSRIA in 2014, states: ‘Luminous flux is the quantity of light emitted by a lamp and is measured in lumens (lm). A 60 W incandescent lamp (formerly commonplace but now obsolete) emits about 700 lm, and a 28 W T5 fluorescent lamp emits about 2600 lm. It can be seen from this comparison that incandescent lamps are less energy efficient than discharge lamps.’
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