Flood beam

Also called wide beam, diffused beam, work light, scene light, flood pattern

A flood beam is a wide off-road light pattern, often forty degrees or more across, that fills the near ground and the sides at the cost of distance, and it belongs low because a wide beam lights a lot of air close to the vehicle.

What is a flood beam?

It is the same light spread over a much larger area. Where a spot concentrates output into a narrow cone to reach a long way, a flood opens the cone up and gives up the reach in exchange for width. Nothing is created or destroyed: the optics decide the trade.

That makes it the right pattern for slow and technical driving, where what you need is to see the ground either side of the tires, the rock you are about to place a wheel on, and the trail edge. It is the wrong pattern for speed, because at forty miles an hour you are outdriving it.

Why a flood belongs low

A wide beam lights a large volume of air near the vehicle, and near the vehicle is exactly where your line of sight passes. Put that volume at eye level and in dust or fog you are looking through a bright wall. Put it below your eyes and you are looking over the top of it at ground that is lit.

This is why the lamp makers put their wide patterns on the bumper. Baja Designs specify their dust and fog, cornering and driving zones low, and recommend that eighty percent of a lighting package stays below the hood line. A sharp upper cutoff makes a wide beam much better behaved in bad air, but it does not license mounting one high.