AF Lock, available in One Shot AF mode
, is an easy-to-use feature that allows you to lock the lens focus of your camera during shooting. Why? To put simply, it gives you the ability to focus on an object, and then recompose your shot freely while still focused on the desired subject.
Popular photographic composition conventions – such as the Rule of Thirds
and the Golden Ratio – suggest that your main subject should not be placed in the middle of your shot. The centre of the frame however, is where the most effective AF point is.
A common technique therefore is to press the shutter button half way down to focus your subject at the centre point, before recomposing your shot with your main subject off-centre.
While this practice is quick and easy, care should be taken to make sure that your subject is actually still focused correctly. This can be a problem if using shorter focal lengths and larger apertures. In those cases, the photographer should get in the habit of switching AF points
, instead of recomposing with AF Lock.