Candlepower (the
antiquated name for
candela,
cd) was a basic
unit of measurement of
luminous intensity, first defined in terms of the amount of
light produced by a pure
spermaceti candle weighing one sixth of a
pound,
burning at a rate of 120
grams per hour.
In 1960 the 11th Conférence Générale des Poids et Mesures redefined one candela as "the luminous intensity, in a given direction,
of a source that emits monochromatic radiation of frequency 540 X 1012
Hz and that has a radiant intensity in that direction of 1/683 watts per
steradian."
Despite being depreciated, flashlight advertisements often describe a product's strength in candlepower.