I've read that the Minox 35's have a leaf shutter, how does this work? I thought it meant that there was a moment when the shutter was completely out of the light path (unlike the 'curtains' that move across on focal plane shutters). If this is the case, why do Minox 35's set their shutter speed to 1/125 sec when a flash is attached. I had a Rollei 35B that would allow flashing at any shutter speed.

-- Jonathan Thron (thron@anl.gov), March 24, 2000

Answers

The difference in flash sync reflects the difference between pure mechanical shutter such as COMPUR and PRONTO vs electromagnetic shutter such as the ones on Minox 35 and Minox 8x11 cameras

The flash sync trigger in COMPUR/PRONTO is achieved by direct mechanical means to close the flash circuit, in other words, it is hardwired.

In electromagnet shutter, the timing of shutter open/close is not controlled by mechanical gears, but controlled indirectly by a electromagnet through a current pulse of various duration. Due to the reactance in the coil, current takes time to reach it speak value, hence the current cannot be straight up and straight down ( Delta function ) --- in other words, there is additional delay due to the reactance of the electromagnetic coil. delay the control of flash sync is not as direct and fast as mechanical shutter. A sync speed of 1/125 leaves more margin for for sync error, otherwise they flash might be missed.

In Minox 35mm, the hotshoe micro switch set the flash sync automatically at 1/125.

-- martin tai (martin.tai@capcanada.com), March 25, 2000.

I assume one reason for the electromagnetic shutter is that it always gets the shutter speed right and doesn't need to be checked up on and 'retuned' every few years like a mechanical one? Of course there's the obvious reason too that this allows the automatic exposure system to work!

-- Jonathan Thron (thron@anl.gov), March 26, 2000.

Electromagnet shutter is smaller, hence used by most compact cameras. The Minox shutter has a tiny electromagnet, won with very fine gage wire.

When Minox shutter "stuck" and repaired, the magnet is the one which often replaced.

Three key points to prolong the life of shutter:

1. Use long exposure sparingly. The load on the magnet by a 5 sec long exposure is equivalent to five hundred exposures of 1/100 sec each. Some people endulged in multiminite long expousre in the dark, sent their cameras to repair more often.
2. Don't put a bare Minox in shirt pocket or trouser pocket, otherwise lint and dust may easily get into the inard of the camera and clog the shutter.
3. Use the correct battery
   
   -- martin tai (martin.tai@capcanada.com), March 27, 2000.