My Favorite Auto-Focus Setting (Revisited)

About a year ago I wrote about my favorite AF setting, and I’m happy to report that I’m as enthusiastic as ever about it.  The basic idea is that I do not want the shutter release to activate the AF system.  On my Canon 30D I

  • activate only the middle AF sensor,
  • choose continuous AF
  • swap the functionality of the shutter-release and exposure-lock buttons by setting the value of custom function 4 to 1.

A half-press of the shutter button now activates the exposure lock and a full-press releases the shutter, a quick press of the exposure-lock button focuses the lens once, a press-and-hold focuses continuously.  So now I have the choice of

  1. manual focus,
  2. single-shot AF,
  3. continuous AF

all without taking my eye away from the viewfinder.  This setting absolutely rocks for street or photojournalistic type of photography.  Plus it’s perfect for portraits because I can focus once, then take a series of images where the subject varies his or her facial expressions, and I don’t need to go through the “focus-then-recompose” before each image.

When I recently got a new Canon 40D, I found out that there is no custom function 4 any more.  Instead there are groups of custom functions, and on the back of the camera there is a new button called “AF ON.”

I’ve been able to achieve a very similar AF functionality on the Canon 40D to that of the 30D by setting C. FnIV-1 (Shutter button/AF-ON button) to 3 (AE lock/Metering + AF start) and C. FnIV-2 (AF-ON/AE lock utton switch) to 1 (Enable).

I recommend these settings wholeheartedly, but if you decide to try them out, plan at least two weeks for the transition and make sure you don’t have any important shoots during that time.  Otherwise you might end up with a bunch of out-of-focus photos…

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