Glad I popped into this thread. I'm supposed to shoot a bunch of art work with a small studio strobe setup I've had for ages but seldom use. So I'd forgotten how they trigger. Fortunately a radio trigger can sit on the camera hotshoe: That triggers one head, the other triggers via a slave. Cumbersome, but it works, and presumably won't fry my camera. I've used it before with my digital bodies, and I've used an big old Metz on them too. Now that I'll have to do some research on.

Radio triggers are the safest. Even the Safe-Sync will let current thru at high voltage levels. I have an old hammerhead flash that puts out over 400V, and that can jump circuits.

Depends, nikons are safe to 250 volts, Some radio triggers (cheap ones) will output more than 6 volts because they have lower QA and just because it works on Nikons doesn't mean it'll work with Canons or Olympuses.

Theoretically, it should work, but in practice it might be something else again. Chances are good that the flash will fire, but e-TTL control or anything other than the sync signal (i.e., HSS, rear-curtain sync, etc.) are unlikely, given that the pin/contact layout is probably quite different. Only the rails = ground and center pin = fire signal are part of the ISO standard for flash hotshoes.

Sync voltage-wise, though, you're liable to be in the safe range, since most of the modern flashes have sync voltages of 10V or less, and most modern hotshoes can withstand around 250V. (The most notorious exception are the first-gen Canon dSLRS (i.e., anything around the vintage of the 300D or earlier which only had a limit of 6V on the hotshoe, hence all the pages and pages of warnings about sync voltage limits).

Actually, the real danger is the other way around. A lot of the cheaper radio triggers can only withstand a few volts. Most of them, like the current crop of speedlights, use a low-voltage signals, but, for example, the Yongnuo RF-602s can only withstand about 11V, and will get fried by older flashes that use much higher voltages. Cactus V5s, iirc, can take up to 300V.

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Yeah looks like 24 V is the maximum for Lumix G :

From UK Lumix Lifestyle website :

Q: Can I use external Flash triggers with the GF1 hot shoe?
A: Yes, however you will need to ensure to use a trigger system with a low terminal Voltage (Less than 24V).

This is for GF1 (my camera) but other G cameras have the same info.

I'm planning to buy two cheap old pentax af200t flash for macro use, and found out this wonderful website with list of trigger voltages of lots of old flash units from various brands that convince me they're safe:

Strobe Trigger Voltage - Is your old strobe safe to use on your new camera