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? > > > > > > > > > > >
