# Fun with shutter speeds and a helicopter **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [December 13, 2008, 6:21am UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996 "2008-12-13T06:21:14Z")\ **Posts on this page:** 7\ **Page:** 2
**Author:** ![Qwakkeddup](https://avatars.discourse-cdn.com/v4/letter/q/90ced4/32.png) [@Qwakkeddup](https://boards.straightdope.com/u/Qwakkeddup)\ **Post date:** [December 14, 2008, 5:14am UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996/21 "2008-12-14T05:14:02Z")
If you watch the blades carefully while the chopper climbs and drops, you can see the rotors changing their pitch, that is essentially how they control the ups and downs. Cool vid. Personally I don’t read any comments to things on youtube etc. The stupid just makes me crabbier than usual. ---
**Author:** ![CutterJohn](https://avatars.discourse-cdn.com/v4/letter/c/91b2a8/32.png) [@CutterJohn](https://boards.straightdope.com/u/CutterJohn)\ **Post date:** [December 14, 2008, 7:33am UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996/22 "2008-12-14T07:33:46Z")
> [@Ale](#): > > The chopper has a constant speed governor, if you think about it, from an efficiency point of view is desirable to maintain the speed of the rotor constant, any changes involve accelerating or slowing down the mass of the rotor. So the governor adjust the engine power and collective pitch of the blades to maintain a stable RPM rate. Less energy needed, less stress on the rotor, better all around. > > Still, a bloody good governor. 🙂 Theres also a hell of a lot of kinetic energy stored in the rotor, and its not maneuvering that hard, so the speed is not going to alter terribly fast. Awesome video though… ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 14, 2008, 3:33pm UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996/23 "2008-12-14T15:33:19Z")
> [@beowulff](#): > > I hate to be pedantic (well, actually, I don’t), but the the frame rate is actually not important other than it needs to be an integer fraction of the RPM of the rotors. The shutter speed needs to be fast to prevent blurring of the blades, but that’s a different issue. Actually, to get _really_ pedantic, the frame rate needs to be an integer fraction of the RPM divided by the blade count. ---
**Author:** ![Henrichek](https://avatars.discourse-cdn.com/v4/letter/h/5daacb/32.png) [@Henrichek](https://boards.straightdope.com/u/Henrichek)\ **Post date:** [December 14, 2008, 4:00pm UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996/24 "2008-12-14T16:00:42Z")
I think they look just lovely with this paintjob: [http://s44.radikal.ru/i106/0807/cd/e6af57dccc83.jpg](http://s44.radikal.ru/i106/0807/cd/e6af57dccc83.jpg) ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [December 14, 2008, 4:18pm UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996/25 "2008-12-14T16:18:36Z")
> [@LSLGuy](#): > > Actually, to get _really_ pedantic, the frame rate needs to be an integer fraction of the RPM divided by the blade count. Hmm… I don’t think this is true. If N is the number of blades. The absolute fastest frame rate that stops motion is equal to the rotor RPM x N. So if the rotor is turning at 1 RPS, and N = 5, you can have a frame rate of 5 FPS and appear to stop the motion, but you will then be seeing each successive blade in the same position. Then, 1, 2, 3, 4, 5 etc. FPS will appear to stop the motion, and in this case, you will see the same blade in the same position. Note that at integral multipliers of RPM x N yields an image that is frozen, but has more blades than reality (10 FPS gives the appearance of 10 blades, for 1 RPS, N=5). ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 15, 2008, 1:52pm UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996/26 "2008-12-15T13:52:25Z")
> [@beowulff](#): > > Hmm… I don’t think this is true. … Good catch. We now agree the blade count is significant, but I short-stroked the actual math. ---
**Author:** ![OtakuLoki](https://avatars.discourse-cdn.com/v4/letter/o/ac8455/32.png) [@OtakuLoki](https://boards.straightdope.com/u/OtakuLoki)\ **Post date:** [December 15, 2008, 2:00pm UTC](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996/27 "2008-12-15T14:00:00Z")
I just want to say thanks, **Johnny L.A.** - I simply giggled through the whole video. 😃 [Previous page](https://boards.straightdope.com/t/fun-with-shutter-speeds-and-a-helicopter/476996.md?page=1)