The rules of horse racing are usually simple: the first horse to cross the finish line wins. But with fractions of seconds separating winners from the rest, determining a winner was an inexact science before photography’s invention. Prior to photography, when two or more horses crossed the finish line together, three stewards stationed at the line would vote on the winner, resulting in arguments and controversy. As organized horse racing—and the betting that went with it—grew during the early 20th century, the ambiguity of close races became an increasing problem. 

The oldest known racetrack photo finish images were made in 1890 by John Charles Hemment, who had earned a reputation for mastering the art of action photography at a time when sedentary subjects were the norm. His photographs were made when a horse broke a thin thread strung across the track at the finish line, triggering the camera’s shutter. With only one exposure, this method often failed to record the precise finish line moment and, if they succeeded, were unable to record the other race placings.

Motion picture cameras had begun be used to record the races in the 1920s, but the frame rate was too low to determine the exact moment the horses reached the finish line. But in 1937, horse racing enthusiast and Hollywood icon Bing Crosby opened the Del Mar Thoroughbred Club and enlisted Paramount Pictures engineer Lorenzo Del Riccio to record the race finishes with his newly-created circular flow camera. First used on Del Mar’s opening day in 1937, Del Riccio’s camera revolutionized finish line photography for horseracing and other professional sports. The immediate popularity of his innovative design had race tracks all over the country clamoring to purchase his patented camera. According to Hollywood legend, Del Riccio was under exclusive contract with Paramount at the time of the invention and it is said that until a deal was reached, the studio pursued him from town to town.

Unlike conventional cameras, Del Riccio’s circular flow camera had a thin, vertical slit that restricts the camera’s field of vision to a four-inch slice of what was before it. The camera is positioned above the track in grandstands and its slit is aligned with the finish line post. Before the horses reach the finish line, the camera begins recording as the strip film moves across the slit at the same rate of the horses as they cross the finish line, recording them from the nose backwards. Only subjects in motion are recorded onto the film; anything static appears as a streak. The film advanced continuously at the same speed of the horses, resulting in images of distorted horse lengths, but accurate in the order of their finishes.

Bertram Pearl improved on Del Riccio’s camera in 1948, incorporating a mirror and neon-pulse time signature in the winning-post. This provided a perfectly aligned image that showed both sides of the horses. The neon showed a set of stripes at 100th/sec intervals for accurate timing. This made it possible to see which horse finished first and by how much. As proof that the camera was not set at an angle, the reflected image of the horses must align vertically with the foreground image exactly. Pearl’s friend and partner, society portraitist Athol Shmith, contributed to the improvements by formulating the means to process the filmstrip in only 55 seconds, and later in just 35 seconds, for rapid review by officials.

Digital cameras are now used for photo finishes, but Del Riccio’s technology is responsible for ensuring fairness in outcomes and by extension, increasing the popularity of horse racing in American culture. Although the circular-flow camera was invented in the middle of the Great Depression when racetracks revenues were low, many tracks chose to spend $300,000 (over $5 million in 2019 dollars) for the cameras. The cameras paid for themselves within a few days of installation as the purses more than doubled due to the security of a scientific, indisputable result. In California, Santa Anita’s “handle,” or total of all bets was $221,537 ($4 million in 2019 dollars) the day before the camera was installed. The following day it was $536,000 ($9.6 million in 2019 dollars). Such was the demand for the scientific certainty that the camera promised to bring to the sport.

While the scientific accuracy of the photo finish has proved reliable, the images themselves depict an alternate reality. The distortions include vanishing horses’ legs and elongated bodies. Stock car race photos show oblong wheels and athletes are depicted as arced smears. Because the strip film moved as roughly the same speed of the racing objects, we are able to see only objects that were in motion as they passed before the camera’s four-inch slit at the finish line. Rather than depicting a location in fixed moment of time as most photographs do, the photo-finish images show a location (the finish line) over elapsed time. Del Riccio was able to conceive of four-dimension photographic technology—length, width, depth, and time—changing the nature of competitive sports.