When High Speed Sync Doesn’t Work on a Canon 50D

After months of consulting multiple manuals, books, forums, and experts, I finally figured out why my Canon 50D + 580EXII flash wouldn’t work in high speed sync mode. That is, when I turned on the flash the maximum shutter speed was 1/250s. No matter what I set the ISO, shutter speed, mode, or aperture to, I could never get shutter speed faster than 1/250s. No matter what mode and settings I applied to the flash and/or camera, as soon as the flash was ready, shutter speed dropped to 1/250s. (I could easily take pictures without flash at speeds faster than 1/250s as lighting conditions and settings permitted.)

If you’re encountering this problem on a 50D (and likely other Canon models) here’s what you (probably) need to do:

  1. Turn the camera on. The flash does not need to be attached.
  2. Press the MENU button
  3. Rotate the Main (top) Dial to select the orange camera menu
  4. Use the Quick Control (back) Dial to select “C.Fn I Exposure”
  5. Press the setting button (the one in the middle of the Quick Control Dial)
  6. Rotate the Quick Control Dial until you see option 7, Flash speed sync in Av mode. You will probably note that option 2, 1/250s (fixed) is selected.
  7. Press the setting button.
  8. Rotate the Quick Control Dial to select either option 0, Auto, or option 1, 1/250 – 1/60sec. auto
  9. Press the setting button.
  10. Press the MENU button.
  11. Press the MENU button.

You can now use high speed sync as advertised.

I think the default is option 0, Auto. However if you’ve ever chosen option 2, 1/250s (fixed), then high speed sync is disabled. I suspect I did this last summer when I was mostly shooting bugs at night, and using flash for main light rather than birds in daytime with fill flash.

For me, this means I can finally use fill flash for bird shots. This is a huge help with backlit subjects, and when you’re looking up at a bird into the sky it’s almost always backlit. These two shots of a Downy Woodpecker demonstrate. The left has fill flash shot through a Better Beamer. The right doesn’t. Both were ISO 400, f/5.6. The left was shot at 1/800s; the right at 1/640s in Av mode.


You can sometimes lighten up the shadows in the non-flashed shot in Photoshop/Lightroom or equivalent if you’re shooting raw and it isn’t too dark, but the sky gets blown out and you pick up a lot of noise. This one didn’t come out too badly, but I still prefer the shot with flash, and many photos are not this salvageable:

Cleaned up backlit woodpecker

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