O'Reilly logo

Canon EOS 40D Guide to Digital Photography by David D. Busch

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

C.Fn III-02: Function of the AF Stop Button on Certain Canon Image Stabilized Lenses

Lens AF stop button function

If you have an upper-echelon Canon image-stabilized supertelephoto lens, you might find an interesting button called AF Stop on your lens. (If you don’t have such a lens, you can skip this Custom Function entirely.) Normally, the AF Stop button does what its name implies: press the button and autofocus ceases. This can be a useful feature that enables you to lock focus when your fingers are wrapped around the barrel of the lens. However, you can change the behavior of this button using this Custom Function setting, as described next:

  • 0: AF stop. Pressing the AF Stop button on the lens locks the autofocus mechanism.

  • 1: AF start. Pressing ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required