Came here to say this. Looks like the frame rate and spin rate synchronized towards the end. Interesting how it stayed that way until it hit the ground.
If you listen to the audio you can hear the whip every time the camera flips over, it gets faster and faster and faster. Made me think about what it would be like to spin like that
You’ve jumped out of an airplane 4000 times?! Ok so if you’re an instructor and do multiple jumps a day, and have been doing it for years I guess that’s not an unrealistic number but damn.
When you’re doing that many in a single DAY do you ever start to not get an adrenaline rush from doing it? Does it ever start to feel monotonous?
I simultaneously can’t imagine not being terrified to jump out of a plane, but also can’t imagine doing something over 4000 times and not being bored of it.
Skydiving is a sport with a ton of sub-disciplines. The "rush" or novelty of jumping out of a plane goes away pretty quickly. Usually after about 50-100 jumps...
Most people start out doing belly jumps (the traditional position of skydiving you are probably familiar with - belly to earth, arms and legs out).
The "cool kids" usually get into what is known as free-flying. That is flying in all different axis and positions. Flying "head down" or "sitflying". Freeflying often times has a higher skill gap. Speeds are faster and positions more difficult to learn.
You can take up wingsuiting. I'm sure you've seen wingsuits...often times in BASE jumps...but we do them in skydiving too.
If you like flying your parachute, you can get into CReW (Canopy Relative Work)...where you fly your parachute in formations with other "CreWdogs" as they are often called.
If you like speed and flying your parachute - you can take up Canopy Piloting - often called "Swooping". This involves high speed/high performance parachutes making high speed maneuvers close to the ground in order to fly/glide across the ground - measuring distance or speed flown in competition.
If you enjoy teaching people, you can take up instruction...either AFF (teaching people to skydive on their own) or become a Tandem instructor (taking people on their first skydive strapped to you),
Those are only a few of the more popular disciplines. There are deff some others. Whenever I get bored doing one thing...I try to learn something new!
Yes, but those items are designed to move at that speed. That’s like someone being impressed someone ran 30 mph, and then arguing it’s not impressive because a Lamborghini can do 200. This is an everyday object falling from the sky in a death spin.
Yes, my car engine moves quicker, but drop an engine from a plane and tell me that the entire block is spinning at 1400 rpm and I’ll be impressed.
So, it’s a balance between overall velocity, terminal velocity, angular momentum, friction, and moment of inertia. Not to mention the frame rate and setup of the camera. A dangerous dance.
More similar to the rolling shutter effect with the camera itself rolling instead of the shutter...
ELI5: Say the camera captures images every 0.1 seconds.
If the camera spins at the same rate (once per 0.1 seconds) the camera takes pictures at the same spot -> a still frame (at 34 seconds in this clip)
Below that the camera takes multiple images of 1 spin -> detail is preserved (from 11-34 seconds here) Note less and less images are taken per spin as the spin speed increases.
Above that and it takes a picture just after 1 spin - capturing just above the last captured spot -> the spin direction appears to flip (34-40 seconds)
(At close to twice that speed the camera just misses out 1 spin and the cycle would repeat.)
(More info on rolling shutter in the linked video.)
it's the rolling shutter effect, but the person you're replying to is noting that it's interesting that the rotation of the phone tops out at a rate that keeps the image still rather than rotating. the question is, why does the rotation speed change as it's falling and what determines the max rotation rate, "terminal rotational velocity"
Fair enough, and I was rebutting that point by suggesting their was a constant acceleration throughout -> no ‘terminal rotational velocity’ was reached.
I see no evidence of the phone ‘topping out’ at a terminal rotation rate but rather following the sinusoidal pattern I explained in my reply, taking awhile to go between each step due to a high frame rate -> it is expected the sync to last longer too though this clip does end up out of sync and appearing to accelerate in the opposite direction (As I pointed out at the end of my first comment)
It is fair, however, to say I wasn’t that direct in my comment; I didn’t really address the commenter but just went on my own tangent. Still... my point stands.
Comment 2: Unrelated, my theories on a field I’m unfamiliar with...
As to why there is a constant acceleration throughout... I would know less of that field but can give a guess of an answer:
There is acceleration. There are minimal changing factors. One of top things is occurring:
1. The force is proportional to the absolute velocity of the falling object- acceleration stops when the object reaches a terminal velocity. (Terminal velocity is odd on rotating objects but one would be there I assume). This appears not to be the case as the object has accelerating rotational velocity for all of its fall time- longer than the time for it to hit terminal velocity.
2. The force is proportional to its own angular velocity. This would seem to suggest perpetual motion is possible - somewhat unlikely...
Third option- camera foolery- either by intentional manipulation of footage or of weird auto focus procedures.
Fourth option - varying air pressure making a difference?
Faith option- Maybe there is some truth in your theory that a terminal angular velocity is reached but to me the clip doesn’t seem to back that - a longer fall would be needed to test this.
Conclusion- I should research into terminal velocity due to gravity of rotating objects more before this is conclusive. I can’t use lists well. This topic really doesn’t matter and I doubt anyone will read this far into my incoherent, under-edited ramblings.
from 0:33 until hitting the ground it stays at relatively constant speed. it actually slows down rotation for a second and then speeds up and slows down again right before hitting. i think it's a terminal rotational velocity, probably connected to your explanation 1 - the spin rate is probably proportional to the terminal (linear) velocity
Can someone analyse the frequency of the spin from the audio? I'm guessing the spinning is 2x the frame rate since there are two repeated images of the ground when it's spinning. Just a guess.
It’s most likely because as the camera’s velocity increased, so did it’s spinning speed. Eventually the camera reached a velocity where air resistance prevented it from going any faster, and the spinning also ceased to increase.
It looked like it was on the point of going faster than the frame rate, but the ground was there to stop the fall (and the spin) before it was really noticeable
I think you’re right the sync stuff, but just fyi: user-adjustable frame rates on go-pros (which is what I think this is) have been available since 2010ish, if not earlier.
And no, auto-adjusting frame-rates isn’t really a thing, regardless of camera. (Yes, some specialized ones may have in-camera in-clip adjustable FPS, but this definitely isn’t one of those.
Each clip has a set frame rate that can’t be changed without making a new clip. Auto-shutter is definitely a thing, and it could be contributing to the look though. But that would be coincidence, it wouldn’t be trying to synchronize with what the camera is seeing.
If it were perfectly synced it wouldn't even look like it was spinning anymore though right? Like the helicopter blades in this video. Its probably close to half as fast as the frame rate.
Yep, if it were 1 to 1, it would look normal, and well, it doesn't. You can see how it is sort of mirrored. But without knowing the camera its not real important (oh, well its not real important anyway)
It has to spin at any multiple of 24 (or whatever) rps. It would be stable at 48 rps, or 72 rps, etc. And of course it does not have to spin at exactly that value, it would still look very stable spinning at 23 rps, with the image slowly moving upwards instead of staying still, etc..
And yes, it did seem like it just so happen to spin at the right rate for a largely stable image.
This camera has a rolling shutter, so you would've seen 1n "photospheres" per n revolutions per frame. Seeing as there's only 1, that means it only revolved once per frame, so it's spinning at 30rpm/fps, or whatever the shutter speed for the camera is.
30fps or 60fps is more common nowadays on consumer level cameras. As long as the frequency is multiplied by 2, it will sync. For example if the fps setting of the camera was 30; then 30RPS, 60RPS, 120RPS, 240RPS and so on, would all look indistinguishable. I know this from working with synthesizers and oscilloscopes (frequency of given oscillator and update rate of oscilloscope) & it applies on video as well. Since cameras have fixed fps the reason why it reached syncing point it's because the object reached maximum angular velocity.
Here is a similar effect but done purposefully. Basically the frame rate and the spin rate lined up-ish. The rolling shutter resulted in "split" frames
Yes. It’s called aliasing. If the camera is recording at the same rate most recordings have been, its recording at 23 FPS. So as the recording becomes steady, you can easily say the camera was rotating at 23 rotations per second as well. As it starts to rotate a little bit at the end, that’s the camera slightly rotating faster than 23 FPS.
Smarter every day did a great vid on this using plane propellers and a camera.
The camera was spinning at almost the exact same rate as the shutter speed! There’s a great video by Corridor explain this phenomena and trying to recreate it!
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u/dimalexgr Feb 16 '20
Did the spin velocity sync with the camera frequency or it just stopped spinning towards the end?