The effect is not image blur but rather a distortion of the shapes. Most visible on old focal plane shutters with a slow travelling speed (and the resulting low flash sync speed) but a 'narrow slot' causing a short exposure (a high shutter 'speed'). A bicycle going through the image will have egg-shaped wheels. I will try to find an example and post a link.
Sven Zitat von Nenad Djurdjevic <[EMAIL PROTECTED]>: > Sven wrote: > "I have always been amazed by the fact that a focal plane shutter this way > does > not capture 'a moment in time' but rather a certain duration in one > image..." > > If that's the way a shutter works at higher than sync speeds (ie. as a > moving slot) then how is it that a moving object is not smeared/blurred > across the frame? > > ----- Original Message ----- > From: keller.schaefer <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Thursday, February 19, 2004 8:04 PM > Subject: Re: AF360FGZ high speed sync > > > > The essence of a focal plane shutter is that two shutter curtains travel > over > > the film plane. For longer exposures (longer or equal the flash sync > speed) the > > first curtain opens the 'window' and lets the exposure begin whereas the > second > > curtain closes it again. For these longer exposures the (electronic) flash > has > > to be synchronised such that it emits its light between these two > actions - > > this is the time when the 'window' is fully open. For shorter exposures > the > > second curtain begins closing the window on one side of the window when > the > > first curtain has not even opened it completely at the other end - > effectively > > a 'slot' is created (hence the German name Schlitzverschlu� - slot > shutter). > > The timing of the two curtains following each other now determines the > width of > > the slot and thus the actual exposure that the film gets. As for these > shorter > > exposures there is no time when the complete film window is free, a > standard > > electronic flash burst would result in only the part of the film being > exposed > > that the 'slot' leaves free (and the rest being dark). > > > > (I have always been amazed by the fact that a focal plane shutter this way > does > > not capture 'a moment in time' but rather a certain duration in one > image...) > > > > The trick with High Speed Sync now is that the flash emits a series of > smaller > > flash bursts that last as long as the 'slot' travels over the film plane. > As > > this distributes the total energy that the flash can emit over time and as > now > > the slot width determines the amount of light that the film gets, the GN > > becomes smaller. > > > > Sven > > > > > > > > > > Zitat von Tanya Mayer Photography <[EMAIL PROTECTED]>: > > > > > Nenad, > > > > > > that makes sense to me - if the shutter speed is faster then less light > > > would be getting in, thus the flash would be less effective? I > think.... > > > > > > fairy. > > > > > > ----- Original Message ----- > > > From: "Nenad Djurdjevic" <[EMAIL PROTECTED]> > > > To: <[EMAIL PROTECTED]> > > > Sent: Thursday, February 19, 2004 4:36 PM > > > Subject: AF360FGZ high speed sync > > > > > > > > > > My flash manual says that as the speed gets higher the flash guide > number > > > > becomes smaller. This is counterintuitive as I would have thought it > was > > > > the other way around. Anyone care to explain? > > > > > > > > > > > > > > > > > > >
