A photo finish occurs in a sporting race when multiple competitors cross the finishing line at nearly the same time. As the naked eye may not be able to determine which of the competitors crossed the line first, a photo or video taken at the finish line may be used for a more accurate check. Photo finishes make it less likely that officials will declare a race a dead heat. Finish line photos are still used in nearly every modern racing sport. Although some sports use electronic equipment to track the racers during a race, a photo is considered the most important evidence in selecting the winner. They are especially important during close races, but they are also used to assign official times to each competitor during any race. Method of capture Strip photography Photo-finish cameras were developed during the 1940s and 1950s as a means of regulating the racing industry and to reduce cheating. Betting on races became increasingly popular during the middle decades of the twentieth century. Authorities were therefore concerned to improve the probity of racing which was widely regarded as corrupt. Typically photo-finish cameras use strip photography, in which a camera is aimed at the finish line from an elevated position in a tower. It captures only the sequence of events on that line in the vertical dimension. Every part of each racer's body is shown as it appeared the moment it crossed the line; anything stationary is represented as a horizontal streak. The horizontal position represents time, and time markings along the bottom of the photo can be used to find the exact crossing time of any racer. The high angle allows judges to see the position of every racer in relation to the others. In a conventional photograph, the image shows a variety of locations at a fixed moment in time; strip photography swaps the time and space dimensions, showing a variety of times at a fixed location. The final image often shows a solid white background, which is a continuous scan of the painted finish line. Racers may appear distorted based on the movement of their limbs and heads as they cross the line; limbs are elongated where they remain static or move backwards in relation to the slit-shutter, or truncated if they move faster than the film moving past the slit. Film Single-exposure photo-finish images were made by a camera that was