T3D Re: Diodes in joined cable releases

[Peter Davis <pd@xxxxxxxxxxxxx>]

John R wrote:

>That's how the Minolta X-700 works (and I suspect most other cameras as
well -
>that way the electrical cable release can be a simple SPST normally open
>switch). The X-700 uses a single conductor for its electrical cable release -
>the outer threaded portion is electrically tied to the camera body (and the
>tripod mount - I just use the metal camera bar (to which the two cameras
>are mounted) as the return path. When the camera is turned on, a positive
>voltage appears on the center conductor of the cable release (relative to
>body ground). If the center conductor is shorted to ground, the shutter is
>triggered. If the shutter is triggered by pressing the shutter button, the
>voltage on the center conductor of the cable release goes to ground a few
>hundred milliseconds later. When two cameras are tied together, pressing
>the shutter button on one will also cause the other to take a photo, but
>after a perceptible time lag. To get good synchronization, an external
>switch is needed.

I bought a twin Ricoh point-and-shoot rig from Alan Lewis, and he had put a
diode in to eliminate cross-talk.  Without the diode, one camera would fire
when the other was turned on, off, etc.  In Alan's configuration, both
cameras were triggered from an external switch.

Recently, I tried a using stereo (3-contact) jacks and just cabling the two
cameras together.  I was hoping to be able to use the shutter button on one
camera to initiate the auto-focus on both, so they would be better
synchronized.  Sadly, the experiment didn't work.  Although I could trigger
the shutters this way, I could not get the autofocus mechanisms to
synchronize.  Anyway, my first attempt at this did NOT include a diode, and
when both cameras one on, one seemed to keep firing at random.

-pd


--------
                             Peter Davis
               Funny stuff at http://world.std.com/~pd

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