8.1 Choice of Light Source
The decision on choice of light source is mainly influenced by:
- efficacy or lumens/watt
- lumens package
- colour temperature
- colour rendition index, Ra.
Other considerations are:
- ability to dim the source electronically (or mechanically)
- lack of auxiliary equipment
- stability of light source colour – with dimming and with lamp life
- lamp life
- compactness of light source – ability to collect the light and project it
- weight of luminaire.
This is a measure of the ability of the light source to convert electrical energy into visible light. It is expressed simply as lumens/watts. One watt of electrical power converted into light of a single wavelength at 555 nm would provide 680 lumens/watt ...