Point to point method
I in cd
1 Calculate E(S) at the distance of d from the light source and incident angle is Theta
Theta is half of the beam angle of the selected flood light
E(S)=
Ɵ
theta
d
Height from floor
I
beam angle
2100 cd
70 deg
Using the polar diagram
Beam angle (deg)
E(S)
Height from floor
Theta
cos(Theta)
d
10 m
35 deg
0.819152
12.2 m
E(S)
11.5 Lux
Horizontal Distance (l)
8.0 m
l
2 Calculate the required luminous intensity if the E(S) and horizontal distance and light mounting height are known;
Height from the floor
Horizontal distance
d
Cos (Theta)
E(S) required
I
Theta
12 m
15 m
19.2 m
0.624695
10 Lux
5906.882 Cd
52 deg
Area
Control Building
Roads/paths
Plant areas
MCC Room
Panel Interior
Intensity (Lux)
320
10
50
300
500