Digital Imaging Global Site – The Power of Imaging

Autofocus (AF) Mode

Autofocus (AF) is the function of a camera to automatically focus on a subject. Most general digital cameras have this function. There are various AF methods, and the available methods are different depending on the model of your camera. Use different methods according to the scene or subject you want to shoot. In the auto shooting modes such as "Intelligent Auto" or "Scene Selection," the AF mode is fixed and cannot be changed.

Autofocus methods

This section explains the AF methods of α series.
Two main AF methods are AF-S and AF-C, and they have different focus operations after the shutter button is pressed halfway down.

AF-S (Single-shot AF)

Autofocus operates when the shutter button is pressed halfway down. Once the subject is in focus, the focus is locked.
It is suitable for shooting motionless subjects such as landscapes or snapshots.

AF-C (Continuous AF)

Autofocus continues to operate and keeps adjusting the focus while the shutter button is pressed and held halfway down.
It is suitable for shooting moving subjects such as sports or railway photography.

AF-A (Automatic AF)

This AF mode is only available in A-mount cameras. When the shutter button is pressed halfway down, the camera automatically recognizes whether the subject is moving or not, and switches the AF mode between AF-S and AF-C accordingly.
Use this mode to shoot various subjects at the same time, or to avoid switching the AF mode manually.

Manual focus (MF)

Manual focus (MF) is the function to let the photographer adjust the focus manually instead of the camera.
Although autofocus (AF) shooting is more typical in digital cameras, MF is effective when focusing is difficult with autofocus, such as in macro shooting.
In MF, you can adjust the focus position by turning the "focus ring" on the lens. Refer to the Instruction Manual or Handbook of your camera for how to switch to the MF mode or detailed operations.

The above is the SEL1855 lens included in the NEX-F3, and the red part is its focus ring. When the camera is set to the MF mode, you can adjust the focus manually by turning this focus ring.

Lens: SAL50M28 / Focal length: 50 mm / F-number: 4.0

The above photograph was shot with the macro lens "SAL50M28." The focus is on the water droplet on the left front side, and the foreground and background are greatly defocused. When you need to adjust the focus precisely to a small area as in this example, using MF is recommended. MF is also useful when the camera fails to find your desired focus position with autofocus.

Focus Magnifier and MF Assist

When shooting with manual focus (MF), Focus Magnifier and MF Assist functions can be used to check whether the subject is in focus. The availability of these functions and their detailed features vary according to camera model. Some models have only one of these functions, but that function can be used to magnify the part of the subject that you want to be in focus, for manual fine-tuning of the focus.
Refer to the User Manual and Handbook for your model to learn about its available functions and details about settings.

[Focus Magnifier] display on the α55. The area in the orange frame is magnified.

Choose 4.8× or 9.5× magnification.

By assigning both Focus Magnifier and MF Assist to buttons or customizable keys, the focus magnification time can be set to [Infinite], which is useful for macro photography and photography of starry skies using a tripod.

Macro photography focus adjustment using MF Assist (NEX-7 camera)