So what on Earth is Back button focusing and why should I use it?
The majority of modern digital DSLR cameras come with default settings in place so you can use the equipment right out of the box. As you become more familiar with it, it’s only natural that you would want to fine tune things to suit yourself, the same way you would adjust your favourite music with the graphic equaliser on your stereo. I think I’m showing my age there.
One default setting is that you have to half press the shutter release button to focus and then fully depress it to take the shot. Most cameras have an AE-L AF-L button on the rear, which is handily placed to be operated with your right thumb, cameras are set up for right handed people, us lefties just have to get on with it and get a grip, literally. The default for this button locks the autofocus and auto exposure together and keeps them locked for as long as you keep the button pressed, this isn’t what we want so by going into the cameras menu and finding the appropriate control, it can be customised to control just the focus, it’ll be marked AF-ON, or at least it is on my Nikon.
There are a few benefits to assigning the AE-L AF-L button its new task –
It’s easier to switch between manual and auto focus – if you use manual focus you’ll find you’re fighting the camera’s autofocus system as the button that controls it is also used to take the shot.
Focus errors can be quickly eliminated – if something in the foreground changes the autofocus may get thrown off however with a quick button press you’re back in focus again and ready to go.
Focus can be locked – One press of the button sets the focus using either the centre point, if you’re using multiple focus points, or the single one, wherever you’ve placed it, this is what I use. Once you’ve released the button the focus is locked on and you’re ready to take multiple shots if you need to, without having to refocus.
You can quickly switch from single to continuous focus – If you keep the button pressed the camera will switch into continuous focus mode which can be very handy if you’re trying to capture things that are moving like a football match or a panning shot of a car in motion.
The question really should be, why would you not use back button focusing, and for that I have no answer.