Before Fresnel developed this lens, lighthouses used mirrors to reflect light out to sea. The most effective lighthouses could only be seen eight to twelve miles away. After his invention, the brightest lighthouses could be seen all the way to the horizon, about twenty-four miles.

The Fresnel lens intensifies the light by bending (or refracting) and magnifying the source light through crystal prisms into concentrated beams. The Point Reyes lens is divided into twenty-four vertical panels, which direct the light into twenty-four individual beams. A counterweight and gears similar to those in a grandfather clock rotate the 6000-pound lens at a constant speed, one revolution every two minutes. This rotation makes the beams sweep over the ocean surface like the spokes of a wagon wheel, and creates the Point Reyes signature pattern of one flash every five seconds.