1.Horizontal dispersion of the luminous intensity
The luminous intensities indicated in Article 2.02 shall apply to all directions of the horizontal plane passing through the focus of the optic or the luminous centre of gravity of the correctly adjusted light source of a vertically positioned signal lantern.
For the masthead lights, stern lights and side lights, the luminous intensities prescribed shall be maintained throughout the horizontal arc within the sector prescribed at least up to within 5° of the limits.
As from 5° within the sector prescribed up to the limit, the luminous intensity may decrease by 50 %; it shall subsequently decrease gradually in such a way that, as from 5° beyond the limits of the sector, only a negligible amount of light remains.
The side lights shall have the prescribed luminous intensity in the direction parallel to the axis of the vessel forward. The intensities shall decrease practically to zero between 1° and 3° beyond the limits of the prescribed sector.
For bi-coloured or tri-coloured lanterns, the dispersion of the luminous intensity shall be uniform so that 3° on either side of the prescribed sector limits, the maximum permitted intensity is not exceeded and the minimum prescribed intensity is reached.
The horizontal dispersion of the luminous intensity of the lanterns shall be uniform throughout the sector, so that the minimum and maximum values observed for the photometric luminous intensity do not differ by more than a factor of 1,5.
2.Vertical dispersion of the luminous intensity
In the event of heeling of up to ± 5° or ± 7,5° from the horizontal, the luminous intensity shall remain at least equal to 80 % in the first case, and 60 % in the second case, of the luminous intensity corresponding to 0° heeling, although it shall not exceed it by more than 1,2 times.