The mechanical "60" uses no circuitry -- indeed, it's the action of the
first curtain reaching the end of it's travel that releases the second
curtain, allowing it to close. With the curtains set to move across the
focal aperture at about 12ms, you get the timing which limits strobe
synchronization to 1/60th second on shutters of this design -- that's
the fastest speed where the entire focal aperture is open at once.
That's why shutters that travel vertically sync faster -- the blades
don't have to move as far before they're "full open".
The circuit that triggers the flash on the 4/2s/et al is battery
dependant -- rather than using blade contacts that close to fire the
flash, they use a (an?) SCR, even in the mechanical setting. We've all
wished Olympus had installed some old mechanical sync switches to go
with the mechanical setting -- they may have even considered it during
design -- but I suspect they decided it was too difficult and costly to
include.
Julian Davies wrote:
>
> Does anybody know if the 2S / 4 have a shutter timer for mechanical 60, or
> does the end of the first curtain run just trigger the start of the second
> curtain run. I'm curious as the speed chosen for mechanical being the X sync
> speed is the only one where one could get away without a timer, but it could
> be complex to arrange the trigger levers.
>
> Julian
>
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