Searchlight, Worklight, Floodlight
In the land of lighting there are different types each for a single or more purposes.
But when it comes to the marine lighting, there can be four main types of lighting specified. navigation lights, signalling lights, interior lighting and searchlights. navigation lights are specified by the Colreg '72 rules and vessels are obliged to follow these rules. Signalling lights can either be continously burning or flashing. Interior lighting, as it says, is used to light the interiors of a ship.
When it comes to searchlights, many people don't know what it is used for. To simplefy matters, DHR divided these searchlights by functionial and technical aspects into three categories: Searchlights, Worklights and Floodlights.
The searchlight is has a very focussed beam with almost parallel rays of light and with a maximum divergence of 10°. The searchlight is used when high visibility at a small spot is needed. For example spotting icebergs, in a search and rescue operation or to light a tow when lights cannot be displayed correctly.
Work lights are more focussed then a floodlight, but less than a searchlight. With a divergence between 10° an 25° it is very useful when a work area needs to be illuminated. For example an excavator on a barge that illuminates where it digs.
When a large area needs to be lighted, like the deck of a large cargo ship or on an oil rig the floodlight does the job. With a beam larger than 25° it lights large areas whit a bright light.