Leaf Shutter High Speed

[Bob Salomon]

The efficiency of the shutter plays into all this. The 1960 edition of the Focal Encyclopedia of Photography defines it as the ratio of the light (the shutter) transmits during the exposure to the amount that it would transmit if it were fully open for the whole duration of the exposure. So a shutter might be open for 1/500 sec. but only transmit the amount of light expected at 1/1000 sec. That shutter would be 50% efficient. The rate of speed the blades or curtains can achieve is the limiting factor. Lower mass blades and higher force improve efficiency. The PQS shutter Bob Salomon cited is a fine example of a high efficiency shutter. In a 50% efficient shutter, lots of activity can be going on that would register as exposure, negating the usefulness of the 1/1000 sec. shutter speed for many applications. My memory is foggy here but Zeiss made a very efficient leaf shutter for its aerial survey cameras by having multiple rotating blades that did not "uncap" till they were up to speed. I remember the surprise I had as a 14 year old seeing the stopping power of a short-duration electronic flash compared to what was possible with ordinary shutters.

The LInhof Aerotronica 70mm aerial roll film camera had a rotary shutter that went to 1/1500. However it required 24V aircraft current and was only hand directable with bungee straps to the empty helicopter doorway.

[mmerig]

The efficiency of the shutter plays into all this. The 1960 edition of the Focal Encyclopedia of Photography defines it as the ratio of the light (the shutter) transmits during the exposure to the amount that it would transmit if it were fully open for the whole duration of the exposure. So a shutter might be open for 1/500 sec. but only transmit the amount of light expected at 1/1000 sec. That shutter would be 50% efficient. The rate of speed the blades or curtains can achieve is the limiting factor. Lower mass blades and higher force improve efficiency. The PQS shutter Bob Salomon cited is a fine example of a high efficiency shutter. In a 50% efficient shutter, lots of activity can be going on that would register as exposure, negating the usefulness of the 1/1000 sec. shutter speed for many applications. My memory is foggy here but Zeiss made a very efficient leaf shutter for its aerial survey cameras by having multiple rotating blades that did not "uncap" till they were up to speed. I remember the surprise I had as a 14 year old seeing the stopping power of a short-duration electronic flash compared to what was possible with ordinary shutters.

There seems to be a contradiction here. Although "there is lots of activity going on" with a 50% efficient shutter, such activity leads to less exposure than if the shutter was 100% efficient, as you mention earlier, so a 1/1000 s speed could still be useful, and even faster.

Your surprise reminds me of when I was a kid, I made a switch out of a can with a balloon stretched over it, like a drum, with foil that actuated an electronic flash. I made pictures of glass bottles shattering as the sound actuated the flash. The shutter was set on B or T, and the bottle was in the dark.

[Havoc]

Let's keep it to mechanical leaf shutters. Otherwise we could wander to Faraday/Kerr cell shutters and other fancy stuff like that. Or Eg&G Microflashes.

[JimboWalker]

Do not rely on higher speed markings!! All of my newer and older shutters are generally one stop slower than marked. Carol Miller at Flutots' repair ( The Best!!) tuned up a Linhof Synchro-Compur for me a month or so ago. 4ooth of sec. is one stop slow. All of the slower speeds are almost right on! In practical use, stay away from counting on higher speed accuracy with any leaf shutter. My Rollei TLR shutter is similar. I never use a shutter speed higher than 60th sec. on my large format anyway, so who cares. The science is informative, but of little practical use in the field.