Canon 7D Wireless Flash Exposure Problem

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UPDATE: The new 1.10 firmware seems to address this problem for me. See: [1]

This page documents a problem I've found with the Canon 7D using the built-in wireless flash transmitter to drive remote flashes. In certain situations, the remote flash fires at too high a power, resulting in an overexposed image. The problem happens with both my 580EX and my 430EX (to a lesser degree). The problem seems to be worst for ceiling bounce cases.

UPDATES:

  • I see the problem on my 430EX as well (previously, I just thought it was the 580EX)
  • This thread reports Canon has confirmed the problem: [2]

If you have any other information, please let me know.

Others appearing to have the same problem:

  • Dpreview: [3] and [4] and [5] (seems to suggest it's a problem with bounced flashes)
  • [6]

To help isolate the problem, I created a test setup where the camera and external flash are tripod mounted in fixed positions. Using a remote flash cable, I can connect the flash (wired) to the camera to compare (a) wired and (b) wireless setups without changing any other factors. This picture documents the arrangement:

IMG 4782.jpg

Camera settings:

  • M mode (manual)
  • 1/100sec shutter, f5.6, ISO 200
  • Firmware version 1.0.9
  • Lens: EF-S 17-85mm (47mm focal length reported in EXIF data)
  • Flash settings
    • Flash MOde E-TTL II
    • Shutter sync. 1st curtain
    • E-TTL II Evaluative
    • Wireless func: external flash only
    • Channel 1
    • Firing Group: A+B+C
    • Exposure comp: 0

Flash settings:

  • ETTL
  • Channel 1
  • Group A


Current Test

Here are the current test images, showing wireless vs wired shots for my 580EX and 430EX in ceiling bounce and direct flash configurations. The wireless cases look consistently over exposed, with the ceiling bounce configuration being the worst over exposure.

In the over exposure cases, I think the external flash is firing at full power or nearly full power, based on the time needed to cycle to be ready to fire again. Also, if I manually set the exposure comp between -2 and -3 (in the camera), the photo is (nearly) correctly exposed.

Setup Wireless Wired
580EX, Ceiling bounce
IMG 0695.jpg
IMG 0697.jpg
580EX, Direct flash
IMG 0696.jpg
IMG 0698.jpg
430EX, Ceiling bounce
IMG 0706.jpg
IMG 0708.jpg
430EX, Direct flash
IMG 0707.jpg
IMG 0709.jpg

Other Things Tried

  • Hard reset of the camera (remove batteries, reset settings)
  • E-TTL II Averaging (vs Evaluative)
  • Setting the flash on group B or C

None seem to address the problem.

Old Test Images

Test Shot #1: 580EX, wired -- correctly exposed
Test Shot #2: 580EX, wireless -- OVEREXPOSED
Test Shot #3: 430EX, wireless -- correctly exposed


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