Intensity of lights

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

I = 3.43 x 106 x T x D2 x K-D


  • I : is luminous intensity in candelas under service conditions,
  • T: is threshold factor 2 x 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:


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.