On 19/04/07, Howard Winter wrote: > Bill, > > On Wed, 18 Apr 2007 08:51:03 -0700, William "Chops" Westfield wrote: > > > > > On Apr 18, 2007, at 7:05 AM, Philip Pemberton wrote: > > > > >>> But why is the prop not blurred? > > > > > > The blur is just > > > because the camera's panning to keep the plane sharp... > > > > Effective panning speed is greater than prop tip speed? > > That seems ... unlikely. Perhaps the stunt includes having > > the motor off :-) > > The prop's angular movement is pretty-much towards the camera, so its movement around its arc is small from the > camera's point of view, while across the frame it's the same as the rest of the aircraft. Fast-revolving objects can > often look odd when photographed head-on - it's not uncommon for one propeller blade to appear heavily curved > while that blade is moving in the same or the reverse direction as the focal-plane shutter, but another blade moving at > right angles is almost straight, however from the side the movement is almost invisible. > > Cheers, > > > Howard Winter > St.Albans, England > I'm not convinced. The prop blur (what little there is) is significantly less than 1/10 revolution. If the shutter speed is 1/2000 sec as previously estimated then at 100km/hr (27.8m/sec) (~minimum speed for this stunt ??) the plane will have moved 28m/2000 = 14cm. If the camera is being panned at this speed to freeze the plane, then the background "moves by" 14cm. But it is blurred much more than that - maybe 10x this amount. The plane may be going much faster, but it won't be going that fast. OTOH Russels comments re the poles moving could be explaned by the air displacement as the plane went past? RP -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist