How is the flash activated on a totally mechanical camera?

[Tuolumne]

I've never even used a flash on an all mechanical camera, but one thing I've always wondered: How is the flash activated on an all-mechanical camera, when there is no electricity to fire the flash?

/T

 

[jke]

There is a contact, often a piece of copper, that gets closed as part of the shutter's actuation. The momentary closing of the circuit that runs from the flash to the PC connector (or hotshoe) and then back (essentially) to the flash causing the flash to fire. You can see this pretty well when looking into a Compur or similar shutter for a medium or large format camera. The electricity comes from the batteries in the flash.

 

[sevo]

Flash well up into the late TTL age and up to 2nd generation DSLRs is triggered by a switch - which does only need electricity at the flash side.

That actually causes some compatibility problems, as recent cameras with flash integration into the camera computer often have safe limits for their electronic flash trigger circuit at 15V or below, while ancient electronic flashes used to be triggered by directly passing the ionizer wire voltage (of 120-500V) across the camera wiper contacts - flashes of that generation will destroy the entire camera electronics of a DSLR or late AF/TTL camera.

Sevo

 

[Dingo]

There is a contact, often a piece of copper, that gets closed as part of the shutter's actuation. The momentary closing of the circuit that runs from the flash to the PC connector (or hotshoe) and then back (essentially) to the flash causing the flash to fire. You can see this pretty well when looking into a Compur or similar shutter for a medium or large format camera. The electricity comes from the batteries in the flash.

To make it simple, the camera acts as a switch, on and off, and a switch itself is a mechanical stuff.