My preferred mode is Aperture Mode. It’s from all these years when the cameras only had aperture priority or manual mode. I’m not saying it’s better, I’m just saying that’s how I think.

Not long after buying my Canon 7D, I bought a Canon 580EXII flash. Load the camera, load the batteries, a couple of test shots. No problem, it seems to be working. Then I turned around, took another photo and all hell broke lose.

The flash fired, but something wasn’t right. Chimping time! Take a look at the LCD. Nothing! Then I hear the mirror slapping down. A 5 seconds exposure. What happened? What did I do? Did I move to the wrong mode? Did I press the wrong button. I try another one, watching carefully what I’m doing, same thing. So I did nothing wrong.

Pull the manual on the computer and I find that yep! That’s the way it’s supposed to work in Aperture Mode. The 7D and the flash will try to balance the exposure. The flash for the foreground, and the shutter speed for the background.

2 solutions

  1. Switch to Tv mode and set the shutter speed mode or
  2. In the Custom Function menu: C.Fn 1 - 7 set the setting to 1 or 2:

When flash is used with aperture-priority AE, this prevents a slow flash-sync speed from being set automatically in low-light conditions.

Canon 7D: Flash sync. speed in Av mode

Canon 7D: Flash sync. speed in Av mode

  • My preference is to leave it at 0 the default. Now, I know what happens with the flash sync speed.
  • Most of the time in flash, I set myself in the manual mode, set a speed of 125 or 250. I set the aperture to fairly wide, or fairly closed depending on the depth of field that I want, and let the flash do its work.

Flash sync. speed in Av mode

  1. Normally, the sync speed will be set automatically within 1/250 sec. to 30 sec. High-speed sync can also take effect.
  2. 1/250-1/60 sec. When flash is used with aperture-priority AE (f), this prevents a slow flash-sync speed from being set automatically in low-light conditions. It is effective for preventing subject blur and camera shake. However, while the subject will be properly exposed with the flash, the background will come out dark.
  3. 1/250 sec. (fixed) The flash-sync speed is fixed to 1/250 sec. This more effectively prevents subject blur and camera shake than with setting 1. However, the background will come out darker than with setting 1.

Manual page: 207