Photo finish

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 are made by a camera positioned at the finish line; this was initially applied to horse racing. The camera's shutter, which captures 136 images each second, is triggered as a horse breaks a thin thread on the race track. All too often, the single-exposure photo-finish camera failed to capture the decisive, first-place finish-line moment. These cameras were only used for first-place finishes, and provided no help in determining any of the other race placings. The oldest single-exposure race-track photo-finish images discovered so far were made by John Charles Hemment in 1890. Historically, motion picture cameras had been used in the United States since the 1920s for recording race-meets but were unsuitable for photo-finish photography as the frame rate was too low to catch the critical instant when horses or dogs reached the finish line. This was achieved by using a special slit camera. Lorenzo Del Riccio, a Paramount Pictures motion picture engineer, improved the circular flow camera, a device which had been invented in the 1930s specifically for the purpose of photographing moving objects. The first racing club to make use of Del Riccio's "Photo-Chart" camera for photo finishes was the Del Mar Turf Club in California at its inaugural meeting in 1937. Unlike conventional cameras, which use a shutter, the circular flow camera uses a single vertical slita strip of film moved horizontally across the fine vertical opening located in the focal plane. This limits the field of vision to no more than a few inches, the restricted field being aligned with the vertical line on the winning post on which the lens is focused. The strip film moves across the slit in the same direction to the race and at substantially the same speed as the rate of movement of the image of the horses as each passes the finishing line. This keeps the image of the horses more or less stationary with respect to the film. As soon as the first horse starts to pass over the line, the camera begins to record its image on the moving film from the nose backwards, progressively along the length of the body, with the arrival of every horse at the finishing post in succession. This produces a strip photographic record of the horses as they pass the vertical plane (winning post). Film is advanced continuously at a pace equivalent to the average speed of a racing horse, resulting in distortions of length (slower-moving horses appear to be stretched), but still preserving the order of finishers. Australian Bertram Pearl made an improvement in 1948 incorporating a mirror and neon-pulse time signature in the winning-post. This provides a precisely aligned image showing both sides of the horses, and a set of stripes left by the neon 100th/sec intervals for accurate timing. Any perfect vertical alignment of the horses' reflection with the foreground image proves the camera is not viewing the finish line at an angle, thus incorrectly recording the horses' relative positions. Pearl's partner was his friend, society portraitist Athol Shmith. Shmith helped accelerate processing of the strip of negative down to 55 seconds, then to 35 seconds. These times rivaled the instant one-minute processing by Edwin Land's newly available Model 95 Polaroid camera. Digital Digital cameras use a 1-dimensional array sensor to take 1-pixel-wide sequential images of the finish line. Since only a single line of the CCD is read out at a time, the frame rates can be very high (up to 20,000 frames per second). Unlike a film-based photo finish, there is no delay from developing the film, and the photo finish is available immediately. They may be triggered by a laser, photovoltaic means, or even motion sensing done within the photo finish camera. Video Another method for creating this strip involves combining individual photographs. A high-speed camera or a movie camera is used to take a continuous series of partial frame photos at a fast rate, while leaving no blank space between the cells. ==Uses==