Candela

Candela (cd) is the SI unit of luminous intensity, used at sea to describe how strong a light appears in a specific direction. In boating, it is most relevant to masthead, sidelights, stern lights, all-round lights and aids to navigation, where the light must be bright enough to be seen at its required range.

A correct candela rating helps other vessels identify your aspect, size and movement at night or in reduced visibility. When fitting or replacing Navigation Lights and Running Lights, check the approved visibility range and fixture type, not just wattage. Candela is directional intensity, while Lumen describes total light output.

Candela sits alongside beam angle, colour, lens quality and power supply when assessing marine lighting. PredictWind forecasts do not report candela, but checking night passages against rain, cloud and Fog forecasts helps you anticipate when compliant, well-maintained lights are most critical for collision avoidance.