A photo finish isn’t just an illustrative expression. Some finishes in racing are so close that only photography is precise enough to determine the finishing order conclusively. A slit-scan camera helped to determine a winner in Sunday night’s AdventHealth 400, the closest finish in NASCAR Cup Series history. Kyle Larson won the race over Chris Buescher by 0.001 seconds at Kansas Speedway.
NASCAR typically uses a radio transponder mounted to the chassis behind the right-rear tire for timing and scoring purposes. However, Sunday’s finish was within the transponder’s margin of error. The electronic system initially declared that Buescher was the winner before NASCAR officially reviewed the finish. On the TV broadcast, fans saw the drivers and crew ride a wave of emotion as they reacted to what they thought was the result before the positions were swapped minutes later.
Steve Letarte and Todd Gordon, race-winning crew chiefs-turned-broadcasters, explained how slit scan cameras work. These high-speed cameras literally have a slit lens, exposing only the finish line to the camera’s sensor as the cars move across the line. The images are collated together to give a complete picture of the finish. The background appears blurred because it’s the same slice repeated across the entire collage. Sometimes, especially when used in cycling or track and field, the competitors can appear squished or stretched when the camera isn’t closely calibrated to the speed of the action.
Letarte and Gordon also discussed Rule 8.5.7.5 in the NASCAR Rulebook, which states what happens if the race is a dead heat after a photo review. The first tiebreaker is the most laps led, followed by the most laps in previous positions until the tie is broken. If all else fails, the winner is who else took the lead first. It’s virtually impossible for a NASCAR race to end in a tie.