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Lamp Mortality
Lamp mortality defines how long lamps are
expected to last. It is expressed as RATED
AVERAGE LIFE in hours of operation. Lamps
usually fail when the filament breaks due
to evaporation or physical shock. There is
a choice of lamp life for incandescent
lamps to suit different installations
where access or maintenance cost can vary.
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gls 1000 hours
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Double Life 2000 hours
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Pluslife 3000 hours
Compared with other lamp types,
incandescent lamps have a relatively short
rated average life.
British Standards BS 161 (IEC 64)
Domestic gls lamps (1000 hours).
BS 6179 GLS lamps (2000 hours).
Colour Rendering
Colour rendition defines how the
light from a lamp affects the colour appearance of objects being
illuminated. It will therefore vary in practice depending on the colours of
the actual objects. However, a generalised approach is that good colour
rendering means the accurate rendition of all colours.
Incandescent lamps have good
colour rendering and people are accustomed to seeing objects under
incandescent illumination. However, incandescent light is biased towards the
red end of the spectrum, so is considered to create a "warm" appearance.
Incandescent lamps have a general
colour rendering index (CRI or Ra) of 100. The colour rendering scale is
from 0 to 100. The topic of colour performance is covered in fuller detail
in a later lesson.
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