On film cameras the trigger mechanism is a contact switch, ie; mechanical.
On digital cameras, the trigger mechanism is usually a semiconductor, thus
the danger of high voltage triggering as the capability of the design can be
exceeded.
There is an IEEE standard that defines what cameras should do, but, it seems
that many of the manufacturers have chosen to ignore the standard, thus the
danger.
Generally, there is a suggestion that 12VDC and below should be safe, but,
best to verify if possible with the actual camera manufacturer.
Use this as a search term in Google, external flash digital camera trigger
voltage
and you will find that a lot of information exists on the net.
I myself use a photocell trigger on my external flash, so in fact, the
camera flashes and then the external flash is triggered, this all happens at
close to the speed of light so it works quite well, and my external flash
trigger cannot then be damaged.
rtt
"The Wop" <the.TakeThisOut@wo.p> wrote in message
news:dgmm53$hea$1@domitilla.aioe.org...
> Hi folks.
>
> I've read that an excessive voltage on the external flash
> hot shoe can wreak havoc on the internal circuitry of a
> digital camera.
> Sync voltages seem to vary quite a lot between flashes. I
> have two flashes. With a voltage tester on I've measured 4V
> on one and 60V on the other!
>
> Does anyone know what is the maximum voltage my hotshoe
> (Fuji finepix S7000) can safely sustain?
>
> Google and the Fuji site haven't helped...
>
> Thanks, The Wop
>> Stay informed about: Fuji S7000: hot shoe and flash voltages