This video, going around the Internet lately, was allegedly shot with the shutter speed synchronized to the helicopter’s blade speed. I thought that shutter speed is a function of still shot cameras, so maybe it’s really synchronized to the frame rate. Photographers, please educate us.
via Urlesque
MarcZero
Is it just me or does that look like a toy helicopter being floated in front of the camera on some string and some sound fx being played along with it. There is nothing else in the video to reference the frame to.
James Schend
“Lately”? That went around the webs 2 years ago. (Well, not that exact movie, someone re-uploaded it. But suffice to say, it’s older than dirt in Internet-time.)
Anyway, film cameras have shutter speed, also. I can’t speak for digital, although I assume it’s the same there… assuming this is a standard film camera, the blades are probably spinning at some multiple of 24FPS (framerate of the camera) / 5 (number of blades).
I’m guessing the camera wasn’t actually synched to the chopper, unless this is some kind of flight testing, but its framerate and the chopper’s RPM just happened to hit the right combination of awesome.
MarcZero: that would be one hell of a detailed toy.
Ivan Lapis
Well, shutter speed is more of a function, rather than a feature in cameras both still and video. It becomes a feature in a point and shoot cameras since the lens and sensor system is pretty much tailored for average users.
Now, shutter speed is the speed of the shutter thus controlling how long the sensor will be exposed for each frame. Now, in video cameras, synchronizing the shutter speed to the speed of the coppter’s blades will produce this effect in the video since the camera will see the blade in the same position for each frame, thus it appears that it doesn’t move… although, it is actually moving, at very high speed actually. The sensor is exposed to see each frame every time the blade is the same position…
James Schend
Oh wait, I see the confusion. Yes, the blades are synced to the camera’s *framerate*, not to its shutter speed. It’s shutter speed is just quick enough to catch the blades without (much) motion blurring.
Daniel Richnak
At first I was pretty convinced that this was real, but then I noticed that at several points the helicopter rotates and you can see a clear shadow of the (unmoving) rotors. This leads me to believe that they are actually stationary, since the shadow is fixed. A toy/model I guess?
Andrew Gingerich
Film/video cameras have both a shutter speed (in celluloid cameras this is referred to as the “shutter angle”) as well as a frame rate, and these two functions can be adjusted independent of each other. In this case, the video was shot at 30 frames per second, but each frame has only been exposed for maybe 1/1000 of a second (imagine a still camera with a very fast burst mode). Because of this quick shutter speed there’s no motion blurring (not even in the shadows, which move at the same rate as the blades themselves), and with a little fine-tuning of the shutter phase it’s a relatively simple task to make the blades appear stationary. (You sometimes see this in car commercials where it looks like the wheels are turning backwards even though the car is moving forwards)
~dan
Richnak:
the shadow moves with the blade so if the blade doesn’t appear to be moving, neither does the shadow.
This is the same effect that you occasionally see in cars that have been filmed and because of the framerate of the camera, the wheels appear to move backwards. Or for that matter, why under artificial lighting (with and alternating current) your wheels seem to turn backwards. It’s a strobe effect. Turn off the lights and wave your hand back and forth rapidly in front of your monitor. If you get the right speed, your hand will appear stationary as well.
~dan
Richnak:
the shadow moves with the blade so if the blade doesn’t appear to be moving, neither does the shadow.
This is the same effect that you occasionally see in cars that have been filmed and because of the framerate of the camera, the wheels appear to move backwards. Or for that matter, why under artificial lighting (with and alternating current) your wheels seem to turn backwards. It’s a strobe effect. Turn off the lights and wave your hand back and forth rapidly in front of your monitor. If you get the right speed, your hand will appear stationary as well.
amanda949
My friend who is a military wife had this to say:
“The blades are turned off. No camera has a shutter speed that fast and it’s a video, not a camera. It’s a military helicopter–they take them up and turn it off to test the helicopter if it were to happen for real and to test the back blades. Really cool to watch in person.”
I’m not sure what to believe, but she has actually seen it in real life, so this could be the truth…?
Camelot
@Amanda949 – sorry, that’s just wrong. If the blades are off then there’s nothing to keep the helicopter in the air and it will drop like a stone.
I can imagine they do turn off the rotors in drills and testing, but this video doesn’t represent that.
Kyle
Uh, no, they don’t just turn off rotors. Pilots have no desire to crash. And even if they did, the helicopter would head STRAIGHT for the ground. It wouldn’t just float around like that.
Either she lied to you or she’s a complete idiot.
I recall that when this video went around on the net a couple of years ago, it was proven to be just a toy model with some bullshit back-story to go with it.
Hans_von_wolfensteinn
@amanda949 It is interesting that your friend says that. It’s partly true and they do test helicopters without power to the rotors but in this video it is clearly not the case and your friend should of noticed. Contrary to some of these other commentators most helicopters will not simply plunge straight to the ground without power because there are failsafes built in. The rotors will not stop rotating even with complete power off. It is called autorotation. The rotors will be powered enough by the rushing wind to rotate them sufficient enough for landing. It is more dangerous and you pretty much can only go down but a trained helicopter pilot should know how to land under these conditions. Just like in these videos http://www.youtube.com/watch?v=4JqmoWAhv5g
Like others have said it is the framerate that has been matched with the blades and it clearly isn’t a toy.
Dyesce
Shutter speed will make the blades look frozen without motion blur.
That the frame rate was just right, I can only imagine to be coincidence, because it would be a huge amount of math just to compute the needed rate.
Very impressive video though, even if it is “as old as dirt” as someone commented.
Andrew J. Winks
It is an example of the stroboscopic effect.
The frame rate of the camera in the video is a sub-multiple of the revolutions per minute of the rotors. We may not be seeing the same blade in the same position each time – we are seeing a different blade caught in the same place. Since the blades are visually the same, we do not notice any movement.
The more blades there are to the rotor, the more likely it is that the speed will synchronise in this way.
Foreigner1
This kind of moviereels were available even before the internet- about as long as camera’s and helicopters have been in eachothers vicinity.
Amanda 949 your friend the military wife as they say in Dutch -loosely translated- has heared a bell sounding but she hasn’t got any idea where to look for the clock that made it sound. Explanation is done by several others here.
jimmytheone
Getting nice motion blur on propellors and rotors is infact quite difficult, particualrly with still photography in most digital cameras,.
Set the shutter speed too low (long exposure) and you’ll get blur but you won’t see it because of the over exposure white out, set the shutter speed higher and you’ll get stopped or worse, “bent blades”.
Most consumer level cameras just don’t have enough of an arpeture setting (f-stop) to balance out the long exposure.
@amanda
“they take them up and turn it off to test the helicopter if it were to happen for real and to test the back blades”, your friend is very very confused.
All helicopter pilots are trained in the event of engine (or gearbox etc) failure to autorotate, that is, the rotors disconnect from the engine and “free-wheel”, it is the free wheeling that creates sufficient lift to get you to the ground somewhat under control.
Autogyros (gyrocopters) in fact use this autorotation as the primary means of lift, an autogyro’s rotor is not connected to the engine in flight at all, the engine uses a propellor to push the aircraft along and the rotors free-wheel to quite a speed and generate the lift to rise, and arrest descent.
If the rotors just STOPPED like the video in real life, you would have a large splat, preceeded by several seconds of terrified screaming and a whooshing sound as you plummet directly downwards uncontrollably to the earth at unsurvivable speeds.
Knota
I’m a photographer and I have to say that Andrew is right for several reasons.
Those of us who do high-speed flight photos know we have to set lower shutter speeds than expected so that we can get blurred propellers on planes to show movement. It take practice and patience.
On top of that, remember there are five blades. If the shutter speed is fast enough, it has about a 20% chance of making it look like it’s frozen in time. That’s a pretty easy to come by chance of making this kind of video.
As for Amanda’s comment, she’s somewhat right as well, but with different words being used. They do test emergency conditions during helicopter pilot training which involves shutting down all power to the rotors(not stopping the rotors). This is a way to test for the student’s emergency training involving “autorotation.” It is meant to stop the sudden descent of a helicopter without power, but does not mean that the blades have stopped, only the engine has stopped. See article: http://en.wikipedia.org/wiki/Autorotation_%28helicopter%29
dingoblue32
blitz
Apr 28th, 2010 at 6:08 pm
“I thought this was common knowledge”
Commom knowlege like what a pigeon looks like??
Or common knowlege like where do babies come from??
Or common knowlege like Algebra??
Sputt
Cool to see the video, but I can’t believe so many have issues grasping what’s going on – or even believe it’s not possible. It’s really very simple and you can see it best in action in a video where you see a helicopter starting up. At first you’ll see the blades moving ‘forward’, then you’ll see them stand still, then they’ll be moving ‘backwards’ – all because of how the blades’ speed correlates to the framerate of the camera. Same with car wheels, or any other rotating object.
Jimmy Sparks
As people above have said, it’s the same as wheels on film, commonly referred to as the wagon wheel effect.
BikerRay
Old news. I’d read that the camera was synched via a radio link so that the blades could be observed under load.
MikeG
Is the rotation speed of the main rotor fixed? I thought it changed to adjust the basic lift of the craft.. or is that done just by rotating the blades along their length?
xadrian
That wagonwheel effect isn’t just for film, your eyes have a “frame rate” as well. You can see stationary wheels or opposite revolutions just by looking at them at a certain speed.
You might also be able to see it on rotors/blades during start up and shut down and likely at certain speeds and angles. It’s never as clean as this, which is why it’s so rare and debatable.
Miss Cellania
The effect of this video wasn’t on purpose. Someone took some footage, watched it, thought the effect was neat, and kept it.
David D
It’s a Balloon.
A big helium filled radio controlled balloon.
That’s my theory anyway.
: )
D
DS
FAKE.First, shutter and frame rate are two very different things. Frame rate is the number of pictures taken in a second (24,30,60, etc.). When the film/video is shown that is broken down back to 24/30 fps and that how slow motion is created. Shutter speed is the amount of time the iris is open for during each one of those frames. (1/30sec, 1/60 sec, even 1/1000 sec).
Shutter speed is like frame rate in that it takes a lot of light, even daylight would look darkened to match the speed of a helicopter. Plus a high shutter makes things look slo-mo or clicker. And that helicopter’s blades would have to be moving at the same constant speed without any minor changes. FAKE.
helimx
I am leaning towards calling this a fake also… I am a helicopter mechanic… though I understand the arguments of the shutter speed, or frame per second speed…. the main rotor systems on helicopters stay pretty close to the same RPM constantly, but not the whole time. A governor is used to control engine to rotor RPM matching, but I don’t think the tolerance is so close that it wouldn’t affect the rotor RPM at all. I would think that the video would show the blades possibly rotating extremely slow, or at the very least, moving back and forth a bit. but, I can say that I have never worked on the type of helicopter in the video, and it is MUCH more complex and sophisticated compared to the helicopters I work on primarily. It is possible the the governors on this particular helicopter are very close tolerance…… so i can’t claim it’s an outright fake….. and I am NOT a photographer by any means, so i can’t use any technical photo terms to prove or disprove it. lol
RickyBeats
This is actually fake. Here is how you know. The heli blades are being controlled by gears inside the heli, guess what? The heli turned, thus, meaning that during the turn the blades would either slow down or speed up ever so slightly during that turn. The fact that the blades stayed “stationary” while the heli made the turns in the video is a dead giveaway that this vid is fake. Sorry to burst anyones bubble. I’m sure “helimx” (see above) can agree with me on this.
Stuart McCracken
A helicopter’s blades likely spin on the order of 5 rotations per second. A typical (consumer grade) video camera shoots on the order of 30 frames per second, and a high-speed camera even more. The only problem that would be encountered is motion blur. So long as your shutter speed is fast enough, you could capture a rotor “not spinning.” As for the blade moving, it does appear to move slightly (more accurately, that it doesn’t appear to be fixed).
If you were lucky, a person could “dial in” the camera to the right rotor speed. If the rotor speed did not change significantly (which is possible), then it would be easy (only problem would be with motion blur). Like what was posted, each frame could catch the rotor move by 1/5 of a rotation between frames. If 1/5 of a rotation is 1/30 of a second, then that means the blade is spinning at 6 revolutions per second. This quick calculation shows that this situation is not unreasonable.
Anyway, if you weren’t lucky but were instead really clever, you be able to synchronize the “shutter” timing to be matched with something from the helicopter. Maybe you could use the “beat” sound of the blade. If it were possible, note that the beat sound would probably be out-of-phase of the actual rotor position (due to sound travel time), but this would make little difference as a change in phase would make the blades move to a different apparent position.
If you were unlucky and more bored than clever, since this is a fairly short video you could hand-pick frames from a high-speed camera to give the proper speed and little-to-no rotor movement. You could find the period of the rotor blade rotation and make a generalization.. e.g. “about 221 frames between regions of interest.” It would be time-consuming, but hardly a week-long effort.
I’m not saying it’s real, but it can’t just be discarded as “impossible” or “FAKE” without being more thorough. Basically, saying it is impossible is saying that “I don’t know how it would be done, so it can’t be done”; that is just being arrogant. All I am saying is that there are ways that it *could* be done, so your premise is not conclusive.
Stuart McCracken
RickyBeats:
If the helicopter was spinning in an opposing direction at 1 revolution in 17 seconds (which it appears to be doing), this would mean a change in 0.059 revolutions per second. If the rotor was spinning at 6 revolutions per second, we’re talking about a 0.9% variance.
Anyway, watch the video particularly right at the end. Keep an eye on one blade and its position relative to the helicopter tail (the “back” two are a good idea). At one point, the tail bisects the space between the back two blades. The setup changes and then one blade is almost parallel to the tail. At the very end the helicopter rotates while the blades do not, returning the setup to the “bisecting” position.
Like I said, doesn’t mean it’s real, but the issues that have been pointed out are more subjective than objective.
CjGuitarist82
No comment to the real/fake nature of the video, but for an easy example of the “Stroboscopic” effect that would have the same result, all you need is a strobe light (with adjustable speed) and a ceiling fan. Turn off the lights and mess with the speed of the strobe light until the fan seems to be staying still (or going backwards, etc).
gdw3
“I’d read that the camera was synched via a radio link so that the blades could be observed under load.”
Don’t know if it’s true, but would explain why the effect would continue with changes in the speed of the rotors.
“That the frame rate was just right, I can only imagine to be coincidence, because it would be a huge amount of math just to compute the needed rate.”
No, because pro video cameras have variable shutter speeds (not frame rates), so you can just dial it in. As you do, you would observe the rotors “slowing down” until they “stop”. As you went past that point, they would seem to begin to rotate in the opposite direction. The aforementioned wagon-wheel effect. I’ve done the same thing myself w/ hummingbird wings. You can dial it in where it just looks like it’s floating with its wings stationary.
As to the comment of it being fake because it would be dark, ….uh, this is shot in broad daylight. There’s plenty of light. You can hardly get a brighter setting. And why would someone invent a function on a camera that couldn’t make a useable picture? Silly.
Karl Uppiano
Judging by the fact that people don’t understand this very simply principle, and seem to lack the imagination to propose how it might be accomplished (camera synchronized by radio to the helicopter, or simply synchronized to the sound of the helicopter) explains why we have people willing to believe in anthropogenic global warming.
Based on this lack of understanding, people are willing to cede their liberty to a power-hungry political elite.
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