Bio15 From Colombia, joined Mar 2001, 1089 posts, RR: 7
Reply 3, posted (7 years 9 months 2 weeks 5 days 20 hours ago) and read 2991 times:
Every time the camera snaps a video frame the blades have turned an angle equal to the angular separation of the blades amongst themselves, or twice that angle, or three times,... It depends on the camera framerate and rotor RPM. What seems as one stationary blade is actually blades 1, 2, 3, 4 & 5 caught in the same position by the camera in fractions of a second. It is also noticeable on the tail rotor which seems to turn very slowly when it really isn't.
Ikramerica From United States of America, joined May 2005, 21636 posts, RR: 59
Reply 6, posted (7 years 8 months 1 week 6 days 5 hours ago) and read 2342 times:
It's not just framerate but also shutter speed. This must be a high shutter speed or the rotors would be blurred anyway. The rotor is going at 6-7 Hz, or 0.14 sec per rotation. So, I'd imagine a shutter speed of 1/1000 second or so could give this effect, matched with a multiple of the fps to keep it from moving too much.
408 rpm would do it, which is a viable rotation speed for a rotor. Or 400 rpm if the footage is from 25fps video or film and not 24 fps film. Both are viable.
Of all the things to worry about... the Wookie has no pants.
N231YE From , joined Dec 1969, posts, RR:
Reply 7, posted (7 years 8 months 1 week 6 days 2 hours ago) and read 2321 times:
I think there is (or was) a thread going in Civ Av about this. The illusion is created by the shutter speed of the camera, and/or the framerate mirroring that of the speed of the rotors. Great illusion!
Sprout5199 From United States of America, joined Feb 2005, 1858 posts, RR: 2
Reply 8, posted (7 years 8 months 1 week 6 days 2 hours ago) and read 2318 times:
Quoting N231YE (Reply 7): I think there is (or was) a thread going in Civ Av about this. The illusion is created by the shutter speed of the camera, and/or the framerate mirroring that of the speed of the rotors. Great illusion!
NOPE, there was a lot of birds in there flapping their wings just after it took off from a conveyor belt.