Section 8 Intensity of lights — International

(a) The minimum luminous intensity of lights shall be calculated by using the formula:

I = 3.43 × 10⁶ × T × D² × K⁻ᴰ

where

I is luminous intensity in candelas under service conditions,

T is threshold factor 2 × 10⁻⁷ lux,

D is range of visibility (luminous range) of the light in nautical miles,

K is atmospheric transmissivity.

For prescribed lights the value of K shall be 0.8, corresponding to a meteorological visibility of approximately 13 nautical miles.

(b) A selection of figures derived from the formula is given in the following table:

NOTE: The maximum luminous intensity of navigation lights should be limited to avoid undue glare. This shall not be achieved by a variable control of the luminous intensity.

(c) All lights, other than a flashing light, shall have a luminous intensity that appears constant and steady.