NASCAR News: Officials explain how close finishes are judged

Sunday’s photo-finish nail-biter between Kyle Larson and Chris Buescher produced the closest margin of victory in Cup Series history at 0.001 seconds, and it raised some questions as to who really won the race because the TV camera images were not real clear.

NASCAR uses a line-scan photo-finish camera and software system called FinishLynx, made by Massachusetts-based Lynx System Developers. FinishLynx has applications in a variety of motorsports series, including IndyCar, Formula 1 and MotoGP, and has also been used in cycling’s Tour de France and in track and field events.

The image from Sunday’s Cup Series finish showing Larson’s No. 5 Chevrolet just ahead of Buescher’s No. 17 Ford is a composite of thousands of tiny, vertical image slices from the start/finish line.

When cars cross the line, the camera captures several thousands of precise, timestamped images per second to create the photo-finish result image. The camera is always on; the image-capture process is activated by the first sign of motion at the finish-line focus point — in this instance, the appearance of Larson’s front splitter breaking the plane to complete the final lap.

That composite image was made available shortly after the checkered flag to the NASCAR control tower, where race officials made the final ruling — per the camera. The finish was so close that timing and scoring data initially showed Buescher ahead because it fell within the transponders’ margin of error – a razor-thin 1.5 milliseconds.

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[The] focal point at the leading edge of the start/finish line cuts through any imperfections in the on-track line painting — which isn’t laser-measured by the grounds crew, and can include checkered-flag designs, track names and/or sponsor logos depending on the event. The physical start/finish line can also be altered by fans writing messages in that area during pre-race track access and the wear and tear of Goodyear rubber from a full field of stock cars crossing it hundreds of times. The camera’s line is the final judge.

See much more at NASCAR.com.