There are three categories of vision in which the human eye functions: (1) photopic vision, experienced during hours of daylight or high levels of artificial illumination; (2) mesopic vision, during dawn, dusk, or when the moon is full; and (3) scotopic vision, achieved when cone cells in the eye do not function. The impact of light on vision is significant in police work, and police officers should be equipped with adequate lighting devices. The current generation of police patrol lights is better than ever, and flashlights are far superior to the flashlights of just a few years ago. Proper techniques for the use of flashlights by police officers are described, including Harries, Chapman, Rogers, and U.S. Marine Corps techniques. Benefits of light-equipped police weapons are listed.