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from the is-a-tenth-of-a-millisecond-faster-than-the-blink-of-an-eye dept.
Velonews reports that a recent Tour de France stage was won by 5mm,
http://www.velonews.com/2017/07/tour-de-france/figure-won-stage-7_443075 which they convert to 0.0003 seconds. The article then goes on to describe the finish line camera:
The judges use a camera placed on the finish line that shoots at 10,000 frames per second. This allows them to confidently pick a winner even when differences are far too small to spot with the naked eye.
...
The cameras don’t work like a normal video camera though. They work more like a scanner.Rather than shoot frames that are thousands of pixels wide using some sort of shutter and digital sensor (the modern replacement for film), the finish line camera is a slit camera. Old slit cameras run film behind a lens. In the timing camera’s case, the design exposes a digital sensor.
A flatbed scanner is a type of slit camera. So imagine pointing one of those at the finish line and scanning the riders coming across. Frame rates can be so high because there is no shutter to close and the cameras only record a one-pixel wide image at a time (10,000 times per second). This type of camera, pointed at a finish line, is guaranteed to show you who or what got to that finish line first, because it shows almost every moment. This is also the source of the distortion we associate with finish line photos. The scanner has a set speed, and anything going slower gets elongated — anything faster gets squished.
No shutter means nothing is missed (because shutters close, and you miss that part). That’s good when the riders are crossing the line .0003 seconds apart from each other.
Anyone know about this technology? Somehow the explanation above doesn't seem all that clear.
[Ed. addition] Maybe one of these recommendations by mrpg might help?
https://gearpatrol.com/2016/07/21/tour-de-france-timed/
https://cyclingtips.com/2012/06/how-time-gaps-are-calculated/
(Score: 2) by wonkey_monkey on Sunday July 09 2017, @08:00PM
I know it's decades old. They used to use it to record panoramas, exposing a thin area of the film as the lens was turned. It's been used in sports since the 60s, I think.
In ye olden days they ran a long strip of film past the aperture, which only lets in a thin of strip of light. That avoids needing a shutter.
These days they could just record "normal" full-frame slow mo video, but that much data isn't necessary and the equipment would be more expensive.
What you end up with is an image of the finish-line evolving over time, stacked horizontally, so the first tire to appear in the image, from left-to-right (or vice versa) is the winner.
systemd is Roko's Basilisk