I kinda hate this article because it could be so much better and yet it isn’t.
The headline is clearly, in some sense, silly. It’s silly because the usual notion people have of fps is something like video where you need to move your roll of film or read out from your sensor at that rate. The ‘frame rate’ for a photo finish is much more incidental to the way the image is made.
If you have an image from a typical digital camera that is 4000px high formed by a typical two-curtain shutter that shutters in 10ms, you expose 400 rows per ms or, in some silly sense, 400k FPS. If you wanted a 1-pixel high slit to be exposed then that’s an exposure of 1/400000s, which is faster than any camera I’m aware of. But I think the analogy is useful – instead of a shutter moving a slit over the focal plane, exposing different parts of the sensor at slightly different times, imagine the sensor being moved behind a fixed slit and then reading out the values from it. You can reasonably easily imagine doing this with film too – just move it past the slit at a steady rate – not dissimilarly from taking an old-school panorama camera and moving the body instead of the lens.
I think the thing happening here is not a moving sensor but rather a 1 pixel wide sensor (or perhaps a few pixels for colour reasons). This makes it thousands of times smaller than the resolution of the final image so even a fairly typical cmos sensor at 2e9 pixels per second could read 50000 pixel ‘frames’ at ‘40k FPS’. (In practice the number would probably be lower for synchronisation reasons). When your frame is very skinny, that still gives you plenty of resolution.
I don’t like the article because they did some silly arithmetic that produces a big number instead of digging into interesting details, e.g.
- talking about how the system works as a whole (when does it decide to start/stop the image, maybe something about buffering)
- talking about how much light you need and how you get enough
- talking about the optics, how you keep everyone sharp while still getting enough light, how you even focus such a thing
- talking how you make sure the camera is setup fairly (eg perpendicular to the lanes, able to get a good view of all the lanes)
- maybe something about reliability and how you avoid the bad scenario of the system failing when it matters most
> You can reasonably easily imagine doing this with film too – just move it past the slit at a steady rate – not dissimilarly from taking an old-school panorama camera and moving the body instead of the lens.
No need to imagine, this is how photo finish cameras at horse and greyhound races have worked for decades.
I agree so much. Not a single mention of what a strip camera is and how the picture we see is not a picture but a composite of 1px wide timestamped slices.
Shame on Petapixel
The track is all white because the finish line is all white. And the Omega/Olympics flag "banner" behind the runners is not a banner, it is a led screen, one pixel wide.
Photo finishes are typically done with a line scan camera. It only captures a single column of pixels at a time. So the horizontal axis in the image is actually time, not space. Super cool stuff.
Outside sports, digital line scan cameras are used in various quality control applications (objects on conveyer belts, vehicle mounted road/rail scanners, etc). This unit can film an 8k px strip at a rate of 80khz.
There is a similar technique in astronomy, though much slower, called drift-scan imaging. Typically when you take a long exposure astronomical image the telescope has to rotate to track the star as it moves across the sky. So in traditional imaging you track the object, make your exposure, and then when the exposure is done you read out the image. The downside is that while you're reading out the image you can't do anything else and for an astronomical CCD it can take on the order of a minute or so. So you lose ~5% of your observing time just to reading out images. (It's more if you have to slew to different locations on the sky.)
In drift-scan imaging you keep the telescope pointed at a fixed location and you continuously read out the image at a rate that matches the motion of the stars across the field of view. This allows you to continuously collect imaging from a strip across the sky.
Oh yeah I took that picture on the Wikipedia article! I have a couple more on my website [1]. One of these days I want to go to Atherton station with my line scan camera to scan some Caltrains.
Fun fact! This is actually how many earth observation satellites work too! Except the motion comes not from the subject, but the satellite orbit itself. It's called a pushbroom camera.
To the question of the Omega logo and Olympic rings asked below, this article states "In fact, the entire photo is literally the finish line viewed one pixel at a time (the Omega and Olympic branding is added at the top)."
I had to combine Tuna-Fish comments and yours to understand what's going on.
> And the Omega/Olympics flag "banner" behind the runners is not a banner, it is a led screen, one pixel wide.
So the one pixel wide scan line camera outputs and image that has time as horizontal axis, and the one pixel screen that draws the omega banner is a 40kfps single line video that does marketing one the photo finish that likely serves as a clock sync check.
Ah I was wondering why you can't actually see the finish line in the image. This wasn't really described well. Are the shadows of the runners artificial then?
Because this is a line camera, the entire image is the finish line. That is, each vertical column of pixels is what was on the finish line at that particular point in time.
That’s also the reason for the distortions. It’s not a single frame taken at one time.
Thanks for pointing that out!
This video doesn't seem to be available in the US, so you can also see it in the slow motion footage here, right on the finish line:
Oh thanks for this! I had the same question and assumed the Omega branding and Olympic rings were superimposed onto the image; I never assumed it would actually be an animated advertisement timed perfectly to match the runners' pace! I assume they had a different backdrop speed for the women's race, according to their projected pace? Or would the ad look squished for them? (or alternatively, the runners stretched?)
Now that I look at it, the logos in the men's photo finish look stretched, so maybe it's calibrated for the women's pace.
They would need to know beforehand the precise span between the first and last athletes.
I think they did a pretty good job, it's only slightly stretched for an event when there was only 0,12 seconds between the first and the last runners, which is unusual.
I don’t see why the distance between athletes has anything to do with it; they record at a fixed speed which presumably is the estimated speed of the winner crossing the line. So it’s known in advance, and the stretch factor if they get that speed exactly right is 1 anyway.
And of course when I say ‘speed’, I mean [width of strip] / [time between the capture of each strip].
I was there at the time, and I could clearly see how the advertising board works. It's a vertical line of LEDs that constantly rotates through the columns of the logo. To the naked eye it just seems to be flickering randomly.
According to Reddit thread on this, the led board behind is specifically animated with the right timing so the content shows up correctly in the line camera.
When I read "line scan camera" I thought of "rolling shutter" which in digital cameras works out to be a horizontal line at a time, which causes interesting artifacts with quick moving objects like propellers or windshield wipers.
Questions that came to mind and answers as far as I can tell:
Q: Are the scan lines parallel to the plane of completion?
A: There is only one scan line and it is parallel to the plane of completion. "In track, the cameras are only focused on the 5 mm near the finish line." [0]
Q: If yes, is the sequence of lines scanned in the same direction as the competitor movement?
A: There is only one scan line.
Note that the rolling shutter effect is not limited to digital photography: it also affects physical focal plane shutters at high shutter speeds due to the time it takes for shutter curtains to move across the frame.
This effect is the origin of the "fast race car slants forward" trope:
First I was wondering why there are ad banners visible in the image. With a line scan camera the background which is standing still should actually only have horizontal stripes.
But since the company Omega produced this photo it actually makes sense to artificially add their logo next to the Olympic rings.
i read that that actually a led screen that basically is synced to the camera so it appears as a 2d banner when in actuallity its a 1d banner that changes over time which when displayed like it is looks like a 2d banner. kinda neat. In a weird way similar to the the adverts painted on the pitch or trackside that look like 2d on screen dogs but only look that way from a certain camera angle
It’s slightly misleading to say it’s time rather than space, though, because of course the subjects are moving and so each column does correspond to a different position (with respect to each one). With respect to the track, however, moving horizontally is obviously just moving in time.
Another weird (until you think about it) thing that’s true: every pixel in the image is at the finish line.
The 'vertical' axis is spatial, representing position across the track, but I would argue that if we take your final sentence and append "...at sequential time intervals" to it, we end up making the case that the horizontal axis in the image is actually time, not space. Each column is the finish line at a different time, and perhaps counter-intuitively (given the usual convention), the right-most column is the earliest.
This is clearer, I think, from considering how the banner is made: as others have pointed out, it is produce by having a single row of LEDs in line with the finish line, each one being turned on and off in a sequence which results in the banner shown in the picture.
Stray gusts of wind, slight irregularities in the track's surface, other tiny inequalities between lanes or starting positions are probably going to nudge runner performance enough to overwhelm the precision of even a fairly unremarkable finish camera.
If fairness were the primary consideration, then they would use any old junk camera and be generous in calling ties. This kind of theatrical accuracy is there purely so that Omega can advertise.
One could say that 1st place only won because some random factor favored him. But one could just as easily say that 2nd place was only so close because some random factor favored him. If there is no way to measure or control a factor, there is no way to know whom it favored.
So race organizers try to make things as fair as possible, but everything beyond that is just “part of the game.” The athletes accept that, and spectators should as well.
I agree with your factual claims, many things can influence the result.
But I don't quite see how using less accurate measuring tools makes sense. At the end of the day getting across the finish line first is the only thing that really matters. Seems to me that more accuracy can only be a good thing
Do they go back to ensure everyones foot is on the block to a precise mm, or to ensure that the runner didn't flinch or move their foot from the block 1/1000 of a second early before the sound hit their ears, taking into account the distance from each runner's ear to the closest speaker playing the starting sound?
The extreme level of precision, I suspect, is not the same at the finish and the start.
They do, in fact, have humans who check to make sure that everyone starts behind the starting line. And both humans and computers which check to make sure that nobody starts early.
Two notes on "starts early." One - start is any visible bodily movement, not the crossing of the start-line. So any flinch, whether in the direction of the start-line or not, is a false start. Two - if you start inside of 0.1 seconds of the start-gun, it is declared a false start, since the assumption is that no human can react faster than that.
The precision at the start is quite high!
The sprinters have speakers near their starting blocks that broadcast the start noise. If this seems excessive, consider that a starting pistol noise takes longer to reach the outer lanes from the inner ones than was the margin between first and second place in this race.
This just illustrates that this specific competition has become meaningless. It might measure their auditory reaction time more than their sprinting speed.
I join millions of other people who find it enjoyable to watch. By that measure it's meaningful. In fact, more meaningful than the _vast_ majority of Olympic events which have less parity and orders of magnitude fewer viewers.
In what way is someone who still finds this event meaningful engaging in irrationality?
Every competition has factors preceding and during the moments of measured performance that are like this. You could also say that a runner’s performance is about their ability to train consistently, apply self discipline to their daily lives, perform under pressure, etc.
It seems odd to me that in the sum of all moments leading up to the start of a race, somehow reaction time would no longer be relevant.
If a runner gets distracted by the crowd, that’s just as impactful to the race but has nothing to do with their potential speed. The race is a measurement of all factors - mental and physical - and all participants are measured the same way.
If a races are decided by such small amounts, like lane 1 being a millimeter ahead than lane 2, then the lanes have to be the same down to a millimeter for it to be a fair race. I wonder if timing will outpace feasible construction before long and we’ll have to say, “lane 1 finished a zillionth of a second ahead, but that makes it a tie because we can’t tell if they started a zillionth of a meter closer.”
That's already the case in swimming, as I commented a few days ago.
It's not possible to build swimming pools to tolerances such that timing to 1/1,000th of a second would be fair (that is, based on athletic performance rather than distance traveled), so swimming events are only judged to the nearest 1/100th of a second. Finishers within the same 1/100th are considered to have tied.
I know it’s vanishingly rare, but in the hypothetical where one swimmer finishes at X.004 and another finishes at X.005, does that mean they will get scored as X.00 and X.01 and not tie despite being only 1/1000th of a second different? I know for normal meets that’s what would happen, but didn’t find an answer in the FINA standards doc for the olympics/world championships.
My read is that any finish within the same 0.01 second is a tie, but a hypothetical finish of, say, 40s.009 and 40s.011 would be ranked 1st and 2nd respectively, despite being only 0.002s different.
The docs I've linked aren't fully clear on this and I've not found official rules.
That is also fair. I think both are fair enough in this rare situation. Whether or not the finish is this close is already luck-based even when two people have equal skill.
As someone who worked closely to the Omega / Swisstiming operations at the Olympics, this is super cool stuff. Congratulations to all involved in being able to deliver when it mattered.
The team also makes really interesting stuff on other sports, such as Beach Volley. Worth checking how it's done.
This is true to some extent. The observation that all 8 runners were within 120ms of each other suggests this sort of hyper-optimization will only continue without really making us better informed. Lyles himself was under the impression that he had come in second, per his on-track interview.
I'm speaking of the mindset, it's the same competitive mindset which leads us to capitalism, and to seeing each other as competitors we have to overpower, instead of collaborators we have to build with
There was controversy in 2012 at the U.S. Olympic Trials when Allyson Felix & Jeneba Tarmoh finished neck and neck -- basically the cameras at the time couldn't make out the difference [0]. I think that was pretty hard on the athletes, so I'm glad to see we've made some progress.
Back in 1987 I started my first job at the Australian DoD. Our group's remit was explosives testing and instrumentation. One of my jobs was to program a hardware controller/sequencer[0] that would trigger numerous equipment: detonators, accelerometer recorders and high-speed analogue cameras. At our facility, we had two bunkers (for in-situ explosives testing), that had a very small window (maybe 15x15cm that was about a foot deep), behind which sat a very big, very expensive, and very fast high-speed camera. That thing could do 10^6 FPS for very short bursts. It had a relatively long lead time to spin up to speed (hence the need for sequencers to precisely kick of the camera and then detonate the subject device at the right moment). I vaguely remember being told that it cost several million dollars (pretty expensive back in 1987). The team that were in charge of that thing also had a couple of Silicon Graphics IRIS workstations, while I was stuck button punching codes on a vertical, rack-mounted keyboard for the sequencer. That camera and the graphics workstations felt like we were living in the future.
I've tried to find out more about the camera but honestly all I can recall is how fast it was, how expensive it was, and that the whole rig took about a square meter or two of floor space. But to eventually be able to see an explosion evolving frame by frame was pretty cool. I fully expect given the pace of change, that by the time 40 years has passed, what was once DoD specced "secret" tech, will be consumer level tech - shrunk from m^3 to several mm^3, and cost down by a factor of 10^5. Amazing.
would have liked to have seen a better explanation of the red lines in the image. it sounds like those are added by humans to outline the runners' chests; how do they ensure the lines are drawn on the frame exactly at the finish line?
If you read the other comments and the article the camera is one pixel wide, each vertical column in the image IS a frame. It's ensured with physics. It's a bit subtle but makes sense once you grok that. So each pixel left is 1/40,000 later
yes, there's literally only one column of pixels, the sensor is say 4k tall by 1 wide, eg a row of pixels.
The x axis in the image (left right) is the time domain.
Imagin instead of the people running from left to right, instead they were still and the pixels were moving right to left, or if that breaks your brain, think about if the track was a people mover and the runners were a static diorama moving left to right and the sensor is just it over time. But also none of that is real.
Does it matter if they're off by ±1 pixel? It's pretty easy to eyeball the rightmost part of each athlete's torso and the frame rate is high enough that there's plenty of space between them.
It looks plenty reliable as long as the camera was positioned and calibrated correctly (which I assume was carefully tested beforehand).
There could be two sets of line, one line assigned exactly when each runner crosses to get his time, and another set assigned when the first runner crosses, and this picture is distributed.
There have been times in the past when photo finish cameras have been installed crooked relative to the finish line painted on the ground [1] and while I have no great love for yet-more-advertising, this does serve to confirm that the camera was pointed in the right direction :)
I have often wondered : Why don't they attach a transponder on each athlete's center-of-chest (using some objective definition) and use that to time each athlete? That can be much much more accurate than any camera.
We can still use cameras for visual confirmation but transponders are much more accurate than any camera.
I'm not convinced they don't. If you look at Lyle's bib when he takes it off and shows it to everyone, there's something on the back. I thought it was another YuGiOh card at first, but then I thought, "That'd be the perfect place to put something to trigger some sort of check at the finish line."
I suspect it's probably just easier for them to print all the race numbers the same way, but only use the transponder on races where it doesn't need to be accurate, or they need to take several measurements throughout the race.
For the longer distances, the lap times and finish times show up almost instantly when there's a big gap between athletes, although I believe there's a laser at the finish line too.
Even if that is technically feasible that wouldn’t account for the lean, neck length etc. the center of the chest isn’t an accurate measurement given the current rules.
The entire photo is the finish line. Look at the color of the ground -- it's cream, the color of the lines on the track, while the track is blue. Each vertical line of the photo is taken in the same position on that finish line.
The first "line photo" is the right-most column of pixels on that photo. The next photo is the second-to-the-right column, etc. This way the winner can be determined as the line first photo that has the contestant's torso in it.
Also every runner in this photo is showing them at the finish line even tho they appear in the photo to be at different places. It’s why all the runners are leaning forward because they are all crossing the finish line.
Nowhere, the camera takes an image of a single line in time (and what the camera sees is the canonical finish line). The visual finish line isn't where that camera is looking, so it's never captured. The left and right of that camera isn't space, it's time (right is earlier, left is later).
The rule is that the winner is the first person whose torso, defined as trunk of the body, reaches the closest edge of the finish line. In practical terms that means shoulder line when leaning forward, as is evident by image in the article.
It would have to be column per second cause cam sensor is most likely rolling shutter so the top of the frame would be detected later than the bottom but ideally if you have a global shutter cam sensor you could do entire frames per second but I don’t think a global shutter 40k fps camera exists.
The image presented is so distorted it makes everyday interpretation impossible. They'd be better off with a mesh of laser rangefinders and a camera shooting at a meager 1,000 fps. They say the winner was ahead by 5 thousandths anyway.
Hmm -- call me crazy, but I feel like the positioning of the camera might have wrongly decided the race for Lyles. The first torso to cross the line wins.
If you look at the still image in the article, Lyles' right shoulder is leaning forward and visible to the camera, positioned to his right.
But Thompson's left shoulder seem to be leaning forward, but is hidden in the camera by his head and neck. It's possible Thompson's left shoulder is ahead of Lyles' right shoulder, but the image doesn't seem sufficient evidence to conclude on that.
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.
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
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.
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.
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.
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.
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 . . .
In Olympic track and field at least two cameras, mounted on opposite sides of the finish line, are required to be used. So the judges had available for their use both perspectives.
My knee-jerk internet reaction was "YOU ARE CRAZY" but then I took a breath and looked at the photo and I can see your argument. There is no point in a runner learning with their left shoulder forward since it will be difficult to place the exact spot behind their heads.
That sounds fine for the Olympics but rather awkward for a lower profile race at which someone just wants to roll a camera out to the track.
The same problem could also be addressed by having two cameras, one on each side of the track, synchronized and recording the same plane.
One could align the cameras into the same plane by putting a vertical array of distinctive marks (e.g. rapidly blinking LEDs) on each camera, above and below the optics and in line with it, such that each camera would see the other’s marks when correctly aligned.
> a vertical array of distinctive marks (e.g. rapidly blinking LEDs)
This doesn't work, as light beams diverge. Even taking a high-quality laser beam with a divergence of 0.1 milliradian (for comparison, a typical laser pointer is about 1-2 mrad), after crossing the 11 meters width of a 9-lane athletics track, you end up with a beam diameter of 2.2 millimeters. At the 10 m/s speed of the athletes and a 40000 fps framerate, they travel 250 micrometers between each frame.
I'm not sure what the issue you're describing is. If I have two devices, each with a camera and a line of marks, if they can each see each other's marks, then they are aligned to within the horizontal spread of the camera pixels. There are no lasers involved -- the marks can be paint, stickers, blinking wide-angle LEDs, etc. -- my suggestion to use blinking LEDs is just so that's it's more obvious when one is in the field of view of the camera.
You don't just need the cameras to see each other, you need them to be perfectly parallel to each other as well, as otherwise they're photographing along a different plane, which may give conflicting results.
Suppose camera A has line L_A on the camera. A’s optics and marks are both on L_A, so A’s image plane contains L_A and camera B’s image plane also contains L_A (you know the latter because you’ve aligned the cameras so camera B sees L_A). And vice versa: camera A sees L_B. In 3D Euclidean space, two distinct lines define a plane, and both camera’s are photographing planes that contain L_A and L_B, so both cameras are photographing the same plane.
More concretely, if the cameras are photographing along different but parallel planes, then they won’t see each other.
Your solution works in a geometric world, where light propagates in a perfect straight line of infinitesimally small width. That's not true in reality, where light propagates in an ever-expanding cone.
More concretely, you can have two cameras photographing along different but parallel planes that do see each other.
High speed cameras usually record into RAM and then dump the recording out to an SSD in slower-than-realtime when it ends. Since the recording duration is limited by RAM capacity they have rolling modes which record continuously into a ring buffer and then store the current contents when the shutter is pressed, so that unpredictable events can be captured after they happen.
Is RAM even fast enough? I remember reading somewhere that the high speed cameras have special cache-like memory on or near the processor that is faster write than RAM. I can't find it now though so I'm taking it with a grain of salt.
The necessary data rate for these photo finish cameras isn't actually that high, because every "frame" is only 1 pixel wide. If the photo is 10000 pixels high, you need a datarate of about 10 Gbit/s at 40000 fps and 24 bits/pixel. RAM is plenty fast enough for that.
Regular high-speed cameras that shoot a video are a whole other story, though.
Maybe my intuition is unusual or wrong, but it seems like a race that's this tight could have been won by anyone. Is being a thousand of a second ahead at a certain point really showing that you are a better or faster runner?
At some point this seems about as fair as a coin toss to me. :)
- To compete in order to see who ran the fastest
- To determine who the best runner is
- To provide entertainment
- To build a career for the runners
- To show the result of the runners' talents, hard work, and dedication
- Build a sense of national pride, ...
My guess is that many people would think of the first point as the "real" purpose of a race. In that case, measuring as accurately as possible makes sense, since it will give the best answer.
If you agree to some extent that races are also about determining who the better runner is - then you must also consider that there is a point after which the runner doesn't control the outcome. Wind seems to be a big factor; the maximum allowed wind is 2 m/s, and the average tailwind for all world records since 1977 is 1.18 m/s (none were made with a headwind). The wind can't be exactly the same in different lanes, so for two very similar runners - there is also a bit of luck involved in the outcome.
> If you agree to some extent that races are also about determining who the better runner is
I don't agree with this to a meaningful extent. "Better" is too vague to be meaningful.
A purpose of the race is to determine who won the race. Sometimes that is to some extent the better runner, but not always. I don't care who the better runner is. I want to know who won the race.
Who manufactured this camera ? this artical is puff brand marketing nonsense ? Anyone got any details on camera manufacturer or similar, actual information?
Even elite marathons now are almost always ending in sprint finishes which is a bit dumb but an obvious problem. The women's olympic marathon was won by less than 3 second after more than 26 miles?
Photos no matter how fast still require human objectivity in evaluation.
Instead there should be some digital signal or laser reflection that is precise?
I don't like the rule where it's any part of the athlete's body first to cross the line, it should be the first athlete to ENTIRELY cross the line, no part of them still remains before the line, not even their trailing foot.
> it should be the first athlete to ENTIRELY cross the line
No, because then you'd be changing the distance of the race.
Runners start behind the starting line. So for consistency, they finish when the first part of their torso passes the finish line.
Your suggestion would only make sense if they started with e.g. their trailing foot touching the starting line and the rest of their body in front of it. But that's not how they start.
Also, if you based it on foot position rather than torso position you'd be introducing a rather random element, since it would change based on what part of their stride they were in. Torso position is much more continuous, and therefore is a far more accurate assessment of athletic ability.
Do they start with their head behind the line? If so that's really running 100m + 1 head. The distance is completely arbitrary anyway so it doesn't really matter.
> Instead there should be some digital signal or laser reflection that is precise?
These photo finishes are really precise. 40k FPS, that's 25 microseconds, or about a quarter of a millimeter in distance (at 10m/s running speed). If you look at it, with the lines drawn, it is very obvious who's won.
The organizers took some time to double check everything since it wasn't obvious from the naked eye, but with the photo finish there is absolutely no ambiguity. In fact, the photo finish is 400x more precise than what is required here.
> I don't like the rule where it's any part of the athlete's body first to cross the line.
It is not the case, the article says the torso matters, not "any part". Also, the athletes stand completely behind the starting line, it makes sense that the race ends just as soon as they touch the finish line, otherwise it wouldn't be 100m but 100m + one body length.
The top two runners in a marathon keep pace with each other, both know that they're holding some energy in reserve for the final sprint. Perhaps one sprinter could try to push themself a little faster throughout the entire race, but I suspect the consequences of running a little over your optimal pace are worse than running a little under your optimal pace, so they err on the side of running a little under their optimal pace and save energy for the final sprint.
This is why world records in long-distance running are not typically achieved at big events, where winning is all that matters.
They are usually attempted at smaller events, coordinating with other runners ("hares") to achieve the perfect pace, without having to worry about the result (hares will typically drop out throughout the race).
If you want to see what happens when the favourites run a little too hard a little too early, check out the 1500m final: Ingebrigtsen and Kerr were supposed to slug it out between themselves, but they both pushed too early (Ingebrigtsen unwisely pulling from the front most of the time), so they got to the sprint too tired to match the surging Hocker.
Yeah, it's interesting to see techniques from short track (skates) or bike track to be used in so extremely different type of run. But after some thought, it's obvious that any long distance run can be divided into phases with different characteristcs and strategies can be built on top of it.
Long-distance running races pre-date cycling and skating by decades. If anything, it's strategies from running that inevitably find their way into more modern sports.
> I don't like the rule where it's any part of the athlete's body first to cross the line, it should be the first athlete to ENTIRELY cross the line, no part of them still remains before the line, not even their trailing foot.
it should be the first athlete to ENTIRELY cross the line
a) Why entirely across, and not just the first to touch the line?
b) I get that basing it on the whole body feels a bit more objective, but it would probably also lead to people diving over the line to gain a few milliseconds. As well as looking a bit silly it could be dangerous. The lean through a (now virtual) tape at chest height is traditional.
I could see bigger people at a disadvantage so is it fair? Please show your work in the form of a myth busters episode, and figure out how to work some form of explosion in.
The headline is clearly, in some sense, silly. It’s silly because the usual notion people have of fps is something like video where you need to move your roll of film or read out from your sensor at that rate. The ‘frame rate’ for a photo finish is much more incidental to the way the image is made.
If you have an image from a typical digital camera that is 4000px high formed by a typical two-curtain shutter that shutters in 10ms, you expose 400 rows per ms or, in some silly sense, 400k FPS. If you wanted a 1-pixel high slit to be exposed then that’s an exposure of 1/400000s, which is faster than any camera I’m aware of. But I think the analogy is useful – instead of a shutter moving a slit over the focal plane, exposing different parts of the sensor at slightly different times, imagine the sensor being moved behind a fixed slit and then reading out the values from it. You can reasonably easily imagine doing this with film too – just move it past the slit at a steady rate – not dissimilarly from taking an old-school panorama camera and moving the body instead of the lens.
I think the thing happening here is not a moving sensor but rather a 1 pixel wide sensor (or perhaps a few pixels for colour reasons). This makes it thousands of times smaller than the resolution of the final image so even a fairly typical cmos sensor at 2e9 pixels per second could read 50000 pixel ‘frames’ at ‘40k FPS’. (In practice the number would probably be lower for synchronisation reasons). When your frame is very skinny, that still gives you plenty of resolution.
I don’t like the article because they did some silly arithmetic that produces a big number instead of digging into interesting details, e.g.
- talking about how the system works as a whole (when does it decide to start/stop the image, maybe something about buffering)
- talking about how much light you need and how you get enough
- talking about the optics, how you keep everyone sharp while still getting enough light, how you even focus such a thing
- talking how you make sure the camera is setup fairly (eg perpendicular to the lanes, able to get a good view of all the lanes)
- maybe something about reliability and how you avoid the bad scenario of the system failing when it matters most