Kelvin The units by which we measure colour
temperatures. Warmer colours such as yellows, oranges
and reds are found toward the lower end of the scale
(2500–3000k)withbluercoolercoloursbeinghigherupthe
scale (over 5000k); daylight is approximately 5600k.
key (main)light In thestudio this isthelight that is
illuminatingthemainsubject;allotherlightsarebalanced
in ratio to this light.
lensspeed Determinedprimarilybythespeedatwhichit
isabletodeliverlighttothecamera;afasterlenswillallow
more light into the camera and thus create the image faster.
lightmeter Adevicewithwhichthephotographerisable
todeterminehowmuchlightisreflectingfromthesubject,
enabling correct camera settings and exposures to be
achieved.
longlens Alenswherethefocallengthislongerthanthat
ofthediagonalmeasurementofthecamerasensorthatitis
shootingwith.Longerlenseshaveasmallerfieldofview
thanotherlenses,andnarrowthescene,aqualitythatcan
bebeneficialinportraitphotographyspecificallybecauseit
slims down a subject. Longer lenses can also create a
shorter depth of field, and can be used to isolate and
highlight a subject from the background.
luminance The quantity of light emitted by a light
source,measuredastheluminousintensityperunitareaof
light from the surface of the source.