Locking focus is one of the most important things to learn with an autofocus camera, especially when making portraits. Locking focus ensures that your subject remains the point of focus as you refine your composition, compose with your subject off-center, or change camera orientation. It’s an important tool to prevent another part of the subject or the background from being in focus, such as the fence that served as a background in this portrait (Figure 4.7).
Figure 4.7 To create a more interesting composition, I posed my subject off-center and used the foliage to balance the entire composition. I focused on him, locked the focus, and recomposed the shot in order to keep him as sharp as possible.
You can lock focus by either holding down the shutter button halfway or pressing and holding the AF start button. If you’ve been using autofocus DSLRs for years, you’ll likely be used to holding down the shutter button halfway. If you find it difficult to do without taking a photograph, the AF start button is a welcome alternative. Not only will it allow you to lock focus, but it also will allow you to engage focus without unintentionally making a photograph.
You can completely separate any autofocus function from the shutter button, which many photographers, especially sports photographers, prefer to do. When you do this, autofocus is activated only when the AF start button is pressed. Locking the focus becomes as simple as releasing pressure on the AF start button. Autofocus will only resume when you reapply pressure to the AF start button. You can then assign the shutter button to meter the scene only when it’s depressed halfway.
To Customize Focus Activation, Follow these Steps:
- Press the Menu button and, using the Main Dial, select the Customer Function 2: Display/Operation menu screen.
- Using the Quick Control Dial, select Custom Controls, and push the Setting button.
- Using the Quick Control Dial, select AF-On, and push the Setting button.
- Select the AF icons on the far left, and press the Setting button.
- Using the Quick Control Dial, select the shutter button icon, and press the Setting button.
- Choose the Metering icon, which appears in the center, and press the Setting button.