Millicandela (mcd) to lumens (lm) 计算器 and how to 计算.
输入 the luminous flux in lumens, apex angle in degrees and press the 计算 button
to get the luminous intensity in millicandela:
For uniform, isotropic 光照 source, the luminous flux Φv in lumens (lm) is equal to the luminous intensity Iv in millicandela (mcd),
times the solid angle Ω in steradians (sr) divided by 1000:
Φv(lm) = Iv(mcd) × Ω(sr) / 1000
The solid angle Ω in steradians (sr) is equal to 2 times pi times 1 minus cosine of half the apex angle θ in degrees (°):
Ω(sr) = 2π(1 - cos(θ/2))
The luminous flux Φv in lumens (lm) is equal to the luminous intensity Iv in millicandela (mcd),
times 2 times pi times 1 minus cosine of half the apex angle θ in degrees (°) divided by 1000:
Φv(lm) = Iv(mcd) × ( 2π(1 - cos(θ/2)) ) / 1000
So
lumens = millicandela × ( 2π(1 - cos(degrees/2)) ) / 1000
Or
lm = mcd × ( 2π(1 - cos(°/2)) ) / 1000
