Photo-finish technology has spawned a handful of articles on how NASCAR determined the winner in a 0.001 second margin of victory at Kansas. I thought I understood the technology, but it turns out I hadn’t quite entirely gotten it.
I was slightly bothered by a post from NASCAR’s Mike Forde because I didn’t understand why it was an ‘image’ and not just a photo.
The Photo-Finish Camera
Cameras have been used to decide race finishes for quite some time. See Zack Albert’s lovely article for a story contrasting the Kansas finish with a back-in-the-day close finish. Original high-speed cameras, were one film, but today are digital.
NASCAR uses a camera made by Lynx. The critical thing Zack included in his article is that the camera is a line-scan photo-finish camera.
I didn’t find a picture on the Lynx page, but to the left is a line-scan camera made by Teledyne.
This kind of camera doesn’t take a full picture. That makes sense because if a camera is going to take a few thousand pictures per second, capturing a slice is all you need.
These cameras collect as little as a one-pixel-wide image. Basically, they capture only one stripe at a time. I’ve tried to illustrate this below. Each picture captures a set number of pixels.
The left-most photo is taken just as the #45’s splitter breaks the plane of the start-finish line. The next one catches next moment in time. And so on.
The Software Part of Photo-Finish Technology
Knowing how fast the photos are taken allows a software program to re-assemble these strips into a composite image, like the one shown below.
The camera technology is used anytime points are award, which means at the ends of stages and the ends of races.
There are a ton of articles about the finish, but this one question was bugging me. I think I have figured it out, but it you know I’m wrong, do let me know!
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This is similar to how an old school “photo finish” system worked. The camera at the S/F line had a narrow vertical slit and the film was pulled past the slit at a high rate of speed as the horse, dogs, cars, runners, etc passed by. The long strip of film was developed and there you had “The Finish”.
Dick
Thanks Dick! That’s a great link between the filmic past and the digital present. Love learning something new. Thanks for reading!