Finding Focus

I’ve heard people lament how the 5D Mark II can shoot in incredibly low light, but not always autofocus when the contrast is poor. There is a little-known but extremely useful trick with most of the Canon DSLRs and the Canon Speedlite external flashes which lets you get around this issue.

If you’ve used a Speedlite on your Canon, you have likely seen the little red grid that the Speedlite casts when trying to focus; the camera seizes on that and can do much faster and more effective focusing even in low light. This is useful, but sometimes you want the fast focusing in situations where you aren’t going to be using the Speedlite.

Most of the Canon DSLR bodies are capable of using the Speedlite only for the focus-assist capabilities rather than for the actual flash. The trick is to leave the Speedlite mounted on the camera and powered on, but disable flash firing in the body.

The function may be in slightly variant places on different camera bodies. For instance, on the Canon EOS 40D the function can be found under the second settings menu (the wrench with two dots), under ‘External Flash’ options; you can disable the flash firing from there. For the Canon EOS 5D Mark II, the option is in the ‘External Speedlite settings’ in the third settings menu (the wrench with three dots), and then in the first flash functions menu. (For the 5D2, this menu is only available when the flash is mounted, as there are some flash-specific options which appear when a compatible flash is present.)

I’ve personally used this technique extensively with a 580EX on both the 40D and the 5D Mark II. I know that this works with the 580EX II as well, and can also be done on the 50D. I’m not certain if the 430EX, or lower-end camera bodies such as the Rebel series, support this trick. (Comment if you know!)

In any case, once the flash firing is disabled you leave the Speedlite mounted and turned on, and the camera will use only the AF assist grid. Your low-light focusing will be immensely improved; I know several band photographers who use this trick for shooting shows without using a flash but still getting quick and sharp focus.

Edit: I have been told that the other Canon Speedlites can indeed also be used this way.

Edit 2: Terence points out, quite rightly, in the comments that the Canon ST-E2 wireless hotshoe remote also can be used this way. If you have an ST-E2, you can simply mount that instead, and take up less space on the camera.


~ by Rachel on February 24, 2009.

3 Responses to “Finding Focus”

  1. Thanks to you, I use this with my 5DMKII with a 580EXII and I can do much more. I wasn’t having that much trouble before, I was using the assist points on the center focus with AI SERVO, but with the assistance of the flash…. its so great. Mostly band photography for me, so extremely low light is my work space and getting fast shutter speeds is needed.

  2. The ST-E2 offers the same function as well, and it’s a lot smaller. Looking at the progression of the speedlights, it would not be a stretch to imagine an ST-E2 Mk II in the works that allows in-body control of TTL ratio-ing. Probably with a metal foot and at twice the MSRP of the existing ST-E2…

    • A good point, Terence. I’ve not used the ST-E2, but it having that ability would make sense. After all, that’s really all the ST-E2 /is/: a TTL solution that lets you fire remote flashes.

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