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Comment by wanderingstan | Hacker News Reader

According to this Reddit thread, the camera actually is the finish line:

> According to UCI regulations, the camera is the finish line.

> The painted line on the road or track is placed there as a visual reference for riders and spectators, and obviously organizers try to align the painted line with the photo finish camera as best as possible. But that's all it is - a visual reference. The finish line is officially defined as the plane of the photo finish camera, not the painted finish line.

https://www.reddit.com/r/bicycling/comments/1emivk1/dont_if_...

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>> UCI regulations, the camera is the finish line

UCI is Union Cycliste Internationale, i.e. the biggest international governing body of cycling events. Not athletics (i.e. track and field). I checked out the C1.1 & C2.1 rulebook from the IAAF and I'm not seeing an equivalent rule. Just a lot of rules for how to place the camera and mark the lane lines and finish line in 19.13

index of all IAAF rulebooks https://worldathletics.org/about-iaaf/documents/book-of-rule...

direct PDF link to the English version of the 17 JAN 2024 C1.1 & C2.1 - Competition Rules & Technical Rules rules (2.5 MB PDF) https://worldathletics.org/download/download?filename=675a00...

Good find! While it doesn’t say it in so many words, this text seems to say a that the camera’s finish line is the official finish line (especially given the implied requirement that the finish camera be a line camera):

> Book C 19.22: Times from the Photo Finish System shall be regarded as official unless for any reason the appropriate official decides that they obviously must be inaccurate.

Woah! Helpful. I guess Thompson should learn to dive forward with his right shoulder next time!

commentators tangentially referenced this when they mentioned that lyles had "learned" how to make a good finishing lunge, but it was also heavily implied that they were talking about the timing of the lunge and not the mechanics.

Yeah, keep in mind at athletics competition, a "false start" is deemed to be anything within 100m of the actual firing gun - because that is deemed to be below the level of human perception, and therefore someone "bet" or "guessed".

So I can't imagine a human can take a conscious step to get a FIVE millisecond advantage over another.

Your comment just made me realize something. The 5 milliseconds which Lyles won by is shorter than the time it takes sound to travel between his lane and Thompson's. If the starting gun were on the outside of the track (it's not), then Thompson would have actually run the race faster, if measured from the time he perceived the sound.

In reality the gun is usually on the inside of the track, so it would be Lyles overcoming this (negligible) advantage.

There's a speaker behind each runner in the starting blocks to avoid that being a factor.

True, but each speaker is positioned slightly differently, because it's immediately behind the blocks but each athlete sets the blocks slightly differently (to accomodate their legs). So in theory...

Tbh, it's all just bullshit to me. Less than 20 years ago, this would have been an ex-aequo, and glorifying someone who happened to dive 5-milliseconds-better is just sad. The obsession with "having a winner", for the benefit of sponsors and image contracts, has taken sports in some ridiculous places.

That's somewhat the nature of sports: the actual results always have some amount of variance. The differences between athletes are often minute enough that with slightly different circumstances the result would have been different. Yet the pressure of a smaller number of contests with outsized prizes does make for dramatic highs when winning for the competitors as well as drama for the spectators.

Of course you can. A good drummer will not deviate from beat by that much.

This doesn’t really answer the question. The camera can only see the non-occluded portions of the plane. Since Thompson’s left shoulder is not visible in the image, we know that his shoulder crossed the image plane at a time at which it was occluded by his head. But without extrapolation, it’s not clear to me that we know when his shoulder crossed the line.

Good point. I guess if you're occluded to the camera, I was assuming the presumption is you haven't crossed the line. But it could still be arguable that he did cross the camera's finish line, it was just occluded.

It doesn't matter when Thompson's shoulder crossed the finish line, since the shoulder is not part of the torso.

The torso was chosen as the body part for determining when a runner crosses the finish line precisely because torsos were easy to identify/distinguish and there is no ambiguity as to a runner's torso.

you don't think shoulder is part of torso?

The exact location of the border line between the upper arm / shoulder and the “torso” would vary depending on the development of the upper body of an individual athlete and would not therefore be totally consistent. Based on anatomy, we can say that the endpoint of the torso is the outer end / articulation of the collarbone (clavicle).

Although the pelvic area is anatomically part of the torso, for consistency in photo finish judging, it is more practical to define the lower end of the torso as the horizontal cross section of the body through the hip line . . .

IAAF Photo Finish Guidelines (June 2015): https://worldathletics.org/download/download?filename=4423f7...

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