Why does a Canon 430EX II overexpose on a Sony RX10, and how should I use it?

Question

I mounted a Canon Speedlite 430EX II on a Sony RX10. The flash fires, so the shoe connection seems to work, but my photos are heavily overexposed. I expected the camera’s auto mode to handle flash exposure, but it doesn’t seem to know how to control this flash.

Does the RX10 need any special setting for a non-Sony external flash, or is this normal? If the flash can only fire but not communicate exposure data, what’s the correct way to use it?

user1943 · Answer

This is to be expected. Without proprietary communication, the camera doesn't know anything like what you suggest with the flash plugged in is way stronger than the dinky little pop-up flash, react accordingly. You will be best off operating your camera in the M exposure mode with fixed settings, and correspondingly changing the power of the Canon flash manually in its manual mode.

This sounds intimidating, but it's not really that hard. For typical indoors, I suggest starting at a shutter speed of ¹⁄₁₆₀th or so, ISO 400, and aperture f/5.6. Take a test shot, and adjust the flash power up or down to suit. You probably want the flash to be at about half power (for faster recharge and less overheating), so you can also change the ISO and aperture as necessary.

Changing the shutter speed won't affect the exposure, unless you make it long enough that the ambient light comes into play. Usually, it's just the short flash burst. Your camera has a somewhat unique advantage, in that it can sync even at the fastest shutter speeds, which is pretty nifty if you are trying to kill the ambient and take flash photos in broad daylight.

But, in any case, if you don't want to deal with any of that, I'd suggest trading it in for a Sony-specific flash.

Why does a Canon 430EX II overexpose on a Sony RX10, and how should I use it?

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