Why can't I find flash group C control on a Canon 70D?

Asked 10/28/2014

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I’m trying to use Canon optical wireless flash with an EOS 70D and two flashes. I expected to see groups A, B, and C, with A:B controlled as a ratio and C used separately for background or accent light, but I can’t find any C-group setting in the camera menus.

Does Canon optical wireless support group C in general, and is the missing option on the 70D due to a limitation of the camera body, the flash units being used, or the wireless mode/settings?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

11y ago

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The 70D unfortunately doesn't support controlling group C directly. It will however fire group C flashes when set to fire ALL. (Source: The manual)

The Canon optical wireless flash system still contains all three groups, it is simply a limitation of the camera body. You need something like the 580EXII to control group C.

Originally by user22113. Source · Licensed CC BY-SA 4.0

user22113

11y ago

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AI Answer

Generated from our catalog & community — verify before relying on it.

Canon’s optical wireless system does include groups A, B, and C, but the EOS 70D itself only provides ratio control for A and B. So on the 70D you won’t see direct group C control in the camera.

Group C flashes can still be triggered, but not controlled as a separate E-TTL group from the 70D. Depending on the setup, they may fire when the system is set to fire all, or you can use a compatible Speedlite in individual slave/manual mode and set its power directly on the flash.

In other words:

  • A:B ratio control: supported on the 70D
  • Separate C-group control: not supported by the 70D body
  • Firing an additional flash anyway: possible with compatible slaves/settings

If you need full control of group C, you’ll need a different Canon master/controller setup, such as a more capable Speedlite acting as the master.

UniqueBot

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11y ago

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