20 November 2014

I rely on autofocus with my Canon G15. In theory you can focus manually at 2× magnification using the LCD screen and the rear control dial, but good luck with that, especially when photographing children.

Despite this, the autofocus controls remained a closed book to me long after I learned to understand and to control aperture, shutter speed, and ISO. Sure, I knew to half-press, reframe, and expose, but that was about it. So, I sat down with a bottle of wine, read the manual many times, then many more times, played with the camera, and finally came up with my own understanding.

Ah, the manual. The information is in there, and I guess the order in which it is presented might make sense to someone, but that someone is not me. So, in the interest saving you some time, and possibly some wine, here is a quick overview.

The three most important autofocus (AF) settings are:

Let’s start with the when settings:

Now let’s consider the where setting, and the interactions with the when settings.

In all cases, camera attempts to focus on whatever is in the AF box. However, the where setting controls how the camera determines the position of the AF box within the scene.

Manual adjustment of the AF box typically involves the AF button (the button marked with ✜ to the upper left of the rear control dial).

If the AF Mode setting is FlexiZone then:

If the AF Mode setting is Face AiAF then:

If the AF Mode setting is Tracking AF then:

In what scenarios might you use these modes? In my mind, the two most important criteria are whether the scene is static or dynamic and whether you wish to focus on faces or not.

I typically leave my camera with AF Mode set to FlexiZone, and both Continuous AF and Server AF set to OFF. However, I configure the shortcut button to toggle Servo AF between ON and OFF.

Some of this should also apply to similar cameras such as the Canon G16 and to a lesser degree to the touch-screen S110, S120 and G7X, but I’ve not checked their manuals to be sure.

See also

© 2014 Alan Watson Forster. All rights reserved.