Lumens (lm) to candela (cd) Calculatrice and how to Calculer.
Entrer the luminous flux in lumens, apex angle in degrees and press the Calculer button to get the luminous intensity in candela:
Candela to lumens Calculatrice
For uniform, isotropic light source, the luminous intensity Iv in candela (cd) is equal to the luminous flux Φv in lumens (lm),
divided by the solid angle Ω in steradians (sr):
Iv(cd) = Φv(lm) / Ω(sr)
The solid angle Ω in steradians (sr) is equal to 2 times pi times 1 minus cosine of half the cone apex angle θ in degrees (º):
Ω(sr) = 2π(1 - cos(θ/2))
The luminous intensity Iv in candela (cd) is equal to the luminous flux Φv in lumens (lm),
divided by 2 times pi times 1 minus cosine of half the apex angle θ in degrees (º):
Iv(cd) = Φv(lm) / ( 2π(1 - cos(θ/2)) )
So
candela = lumens / ( 2π(1 - cos(degrees/2)) )
Or
cd = lm / ( 2π(1 - cos(º/2)) )
