Olympus cameras are well-known for their configurability. Autofocus is probably one of the most configurable features of these cameras. In fact, discussing every possible option for autofocus will probably require a book! Therefore, in this article, I will (ehm) focus on back button focus and how to set up your OM-D E-M1X or E-M1 camera for back button focusing. Let me tell you all about it.
Back button focusing?
Normally, auto-focus is activated by half-pressing the shutter release button. However, there is a popular alternative technique called back button focusing, which uses the AF lock or AEL/AFL button (depending on the camera) to activate autofocus. This can be used either in conjunction with shutter half-press, or disabling the half-press AF. The options you have depends on your camera, but I'll assume you own an Olympus, in which case all of these options are available.
Back button focus allows the photographer to activate and, more crucially, deactivate autofocusing independently of the shutter release. Although it requires a bit of practice, it is a very powerful technique. On Olympus cameras, it is particularly powerful thanks to Olympus' support for instant manual focus override in all AF modes.
All AF-related options are located in the A menus in the Custom menu (cog icon). To configure the camera for back button focusing, we will change the options in the A1 menu, under AEL/AFL configuration.
The AEL/AFL options contain four items you can change. S-AF, C-AF, MF, and Half Way AF.
Under S-AF, we set the behavior of the AEL/AFL button in S-AF (single auto-focus) mode. This option has three modes. The mode3 setting will change the camera so that the AEL/AFL button will initiate single auto-focus.
Under C-AF, we set the behavior of the AEL/AFL button in C-AF (continuous auto-focus) mode. This includes continuous tracking auto-focus as well. There are four modes, of which we will use either the mode3 or mode4 setting, which make the AEL/AFL button auto-focus while pressed. The difference between the two modes is in the behavior of the full shutter release, and whether it will lock the exposure (mode4) or not (mode3).
Under MF, we configure the AEL/AFL button as used in the MF (manual focus) mode. Here we will set it to mode3, which activates single autofocus (S-AF) when AEL/AFL is pressed.
Additionally, we can disable AF on half-press by setting the Half Way AF option to Inoperative. This means that when we half-press the shutter release, the camera will not auto-focus. This gives the AEL/AFL button exclusive control over AF activation.
There is a feature that can be very useful in combination with back button focusing. In the A1 menu, go to AF+MF and turn it On. This will cause the camera to show an "MF" label next to S-AF, C-AF and C-AF+TR options in the focus modes selection and enables the instant manual focus override in all AF modes.
How to shoot with back button focus
To shoot with back button focus, we shoot pretty much as we normally do, except that we press (S-AF) or hold (C-AF/C-AF+TR) the AEL/AFL button to acquire focus or track a target.
Unlike half-press AF, with back button focus you have to use the thumb to activate AF and change the focus point by default. This can sometimes be a problem if you want to change the focus point on the fly. To address this, you can reconfigure the button layout to use a different button as AEL/AFL (for example one of the front function buttons or the L-Fn button on the lens if your lens has it).
When you want to switch to manual focus, simply release the AEL/AFL button. Now the camera is practically in manual focus mode.
The focus mode to rule them all
Once you get the hang of this camera configuration, you will notice that you don't really need three focus modes. Yes, the C-AF mode (or C-AF+TR) becomes the ultimate do-it-all mode:
- S-AF: press the AEL/AFL button until you get focus and then release it
- C-AF: hold AEL/AFL
- MF: don't touch the AEL/AFL at all
This can dramatically speed up the workflow if you normally frequently switch between focus modes.