10/ 2010
BENNING LUXMETER B
22
3.7 What is cosine correction?
Light falling at an angle on an object tends to be increasingly reflected as the
angle of incidence increases. This causes illuminance meters to read too low
when measuring light falling obliquely, unless a cosine correcting mount or a
cosine diffuser is used in the meter head assuring an angular response close
to the cosine function.
Observed surface
Einfallswinkel (°)
Abbildung 4:
Kosinuskorrektur
Θ
= 8 5
Ο
9 %
Θ
= 0
Ο
1 0 0 %
Θ
= 3 0
Ο
8 7 %
Θ
= 6 0
Ο
5 0 %
100
80
60
40
20
-70 -50 -30 -10 10 30 50 70 90
Θ = angle of incidence
Relative responsitivity
