Clause 8 Intensity of lights
Maritime Rules Part 22: Collision Prevention
(1) The minimum luminous intensity of lights must be calculated by using the formula—
I = 3.43 × 10⁶ × T × D² × K⁻ᴰ
Where | I is luminous intensity in candelas under service conditions; and |
T | is the threshold factor 2 x 10-7 lux; |
D | is the range of visibility (luminous range) of the light in nautical miles; and |
K | is atmospheric transmissivity. |
For prescribed lights, the value of K must be 0.8, corresponding to a meteorological visibility of approximately 13 nautical miles.
(2) A selection of figures derived from the formula is given in the following table:
Range of visibility (luminous | Luminous intensity of light in |
range) of light in nautical | candelas |
miles | K = 0.8 |
1 | 0.9 |
2 | 4.3 |
3 | 12 |
4 | 27 |
5 | 52 |
6 | 94 |
Note: The maximum luminous intensity of navigation lights should be limited to avoid undue glare. This must not be achieved by a variable control of the luminous intensity.