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I'm trying to get to a definitive answer here and wondering if anyone knows for sure.

I have an old Canon 430EX II flash I'd like to fire as a slave from my Powershot G7X Mk II. Whilst it is technically an optical slave and both are Canon, I'm not sure that one can actually trigger the other - can anyone confirm for sure?

And if this won't work - do you have any recommendations for external flashes I can use as a slave from my G7X MK2?

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It won't work without additional gear.

The 430EX II does indeed have optical wireless capability, but only in Canon's "smart" optical system. That requires a master unit that can "speak" the optical light-blip code that is how that communication protocol works. The pop-up flashes on the T3i and later T#i, ##D, and 7D bodies can do this. But built-in flashes on the the Canon Powershots, like the T# and SL# and lower-end Canon mirrorless bodies, can not.

And the 430EX II doesn't do "dumb" optical (typically called S1/S2 on a lot of 3rd-party flashes) triggering, like a Nikon SB-700 can with its SU-4 mode. And attaching a "dumb" optical trigger to a 430EX II's foot or cabled to a sync adapter on its foot is problematic, because the Canon EX speedlights never played well with most optical slaves. Something like a "Wein peanut" isn't going to work; you'd need a Sonia green-based optical slave. But buying one and a sync adapter for either PC or 3.5mm is going to cost roughly the same as just buying a cheap manual speedlight (like a Godox TT600) with S1/S2 modes built-in.

Keep in mind, this is very limited triggering capability. All you can tell the flash to do is fire. There's no TTL or HSS, any settings changes have to be done directly on the flash (so make sure it has M mode and physical UI controls for power/zoom/etc. settings).

However. Most compact fixed-lens cameras do use a leaf shutter, so HSS is kind of a non-issue. And my experience triggering my S90 with an optical slave leads me to say, use S1 if your camera is in M mode, and S2 if your camera is in Av/Tv/P/Auto modes to get the sync timing correct. S1 fires the flash on the first burst it senses; S2 on the second burst to avoid firing early with a TTL metering pre-burst. Canon apparently likes to do something with a metering pre-flash in those exposure modes, and typically doesn't give the Powershots any ability to switch the built-in flash from TTL to M.

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  • \$\begingroup\$ Superb answer, thank you inkista - that's exactly the detail I've not been able to find anywhere and has sorted me huge amounts of faff and trawling. Thank you! \$\endgroup\$
    – Ben
    Jan 27, 2022 at 9:44
  • \$\begingroup\$ you can use a peanut, problem is they can be weak. Tape the peanut right up to the on-camera flash and use a PC extension to feed a hot-shoe. Worked perfectly for my 550EX when using it "normally" was very unreliable. I also think even the 4xx series trigger just by connecting two pins on the hotshoe, which means you could easily wire up something yourself to do that, like an n-channel mosfet's drain+source tot he show pins, then fed to the gate+source by a solar cell fed by the on-camera flash... \$\endgroup\$
    – dandavis
    Jan 29, 2022 at 9:59
  • \$\begingroup\$ @dandavis "...Tape the peanut right up to the on-camera flash and use a PC extension to feed a hot-shoe..." except that a peanut, a hotshoe to PC adapter and, say, a 10' PC cable would cost more than a Godox TT600. And if you are going Rube Goldberg up a peanut-in-front-of-the-built-in flash setup, you can plug the peanut into a radio transmitter sync input and have a radio-based wireless solution. I did that with a Sonia peanut, Yongnuo RF-602 triggers, and my S90. \$\endgroup\$
    – inkista
    Jan 30, 2022 at 6:45

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