8. Intensity of lights
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Statutory Documents - IMO Publications and Documents - International Conventions - COLREGS - International Regulations for Preventing Collisions at Sea - International Regulations for preventing Collisions at Sea, 1972 - Annex I - Positioning and Technical Details of Lights and Shapes - 8. Intensity of lights

8. Intensity of lights

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

where
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:

Range of visibility (luminous range) of light in nautical miles Luminous intensity of light in candelas for K = 0.8
D I
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 shall not be achieved by a variable control of the luminous intensity.

Parent topic: Annex I - Positioning and Technical Details of Lights and Shapes
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