Why does my Yongnuo flash exposure get darker as I zoom in on Canon E-TTL?

Asked 5/9/2018

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I’m using Yongnuo YN568 speedlites on Canon 5D Mark III and 6D bodies with a Canon 24–70mm lens. In E-TTL, flash exposure looks correct at the wide end, but as I zoom in to around 50mm or 70mm the image gets progressively darker. This happens with multiple Yongnuo flashes on both cameras, so it seems unlikely that all of the flashes are faulty. Is this a known compatibility or metering issue, and is there a setting change that fixes it?

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

Photography Stack Exchange contributor

8y ago

2 Answers

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All my Yongnuo's act the same..surely this cannot be a fault in all 3. I am sure I am doing something wrong.

Well, it kind of is a known issue with Yongnuo flashes when using Canon's Evaluative Metering.

Switching main metering to Center Weighted Average, Partial, or Spot metering modes and changing the menu item [Shooting (Red Tab with camera symbol) Tab 1→External Speedlite Control→ETTL II Flash Metering] from Evaluative to Average usually resolves the issue.

Originally by user15871. Source · Licensed CC BY-SA 4.0

user15871

8y ago

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AI Answer

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Yes — this is a known issue some Yongnuo flashes can have with Canon’s E-TTL II when using Evaluative flash metering. The darker exposure as you zoom in is usually not a zoom-head fault, but a metering/compatibility quirk.

A common fix is to stop using Evaluative metering for flash and switch to averaging-based settings instead:

  • On the camera, go to External Speedlite Control.
  • Change E-TTL II Flash Metering from Evaluative to Average.
  • If needed, also use Center-Weighted Average, Partial, or Spot for the camera’s main metering rather than Evaluative.

Those changes often restore more consistent flash exposure across focal lengths. Since all three flashes behave the same way on both bodies, that strongly points to a system compatibility issue rather than a defect in each flash.

UniqueBot

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8y ago

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