Question: Should I just shoot in my automatic autofocus mode or is it best to select a different one? Could you explain to me what they all do on my camera?
Answer: Getting your subject perfectly sharp is absolutely vital to the success of a shot. It’s most challenging when shooting with very wide apertures where the depth-of-field is extremely shallow, or with fast-moving subjects where the point of focus is constantly changing. Most DSLR focusing systems work slightly differently to those found on CSCs, but both are similar in that the frame is divided up into focus areas or focus points. These can range from nine on basic models, to over 200 on pro cameras. By choosing how you want these areas or points to behave, you can give yourself the best chance of achieving a sharp image. Or you might opt to turn them off entirely and focus manually for maximum accuracy. Here we take a look at the different focusing modes, and why they’re best for certain types of picture.
Understanding the four main camera focusing modes...
One-shot AF/Single Servo AF
The camera will acquire focus only once when the shutter button is half-pressed. Usually, this is using just one AF point, though some cameras allow a cluster of points to be used. Most photographers prefer to select this point themselves, which allows pin-point focusing ideal for portraits and landscapes. Alternatively, auto-area AF forces the camera to choose the point automatically, usually selecting the object closest to the camera.
AI Focus/Automatic AF
In this mode the camera automatically detects whether the subject is moving or stationary, and selects either AF-S (one-shot AF) or AF-C (AI servo). This is a good mode to use if your subject is mostly stationary, but might move unexpectedly, such as a deer or a child playing. If you’re not comfortable switching between the two main focusing modes, this is the best option to use to get started.
AI Servo/Continuous AF
With the shutter button half-pressed, the camera continually acquires focus, which is ideal for any subject that moves towards or away from the camera. In this mode you can either have just one active AF point, which will keep whatever covers this part of the frame sharp, or choose a larger group of points. You can also activate 3D tracking, which will keep your subject sharp wherever it moves within the frame.
As fast and accurate as modern autofocus systems are, there are occasions when you’ll get more accurate results with it turned off. If you’re into night sky or macro photography, for example, you’ll work almost entirely in manual. For really accurate results, activate Live View, use the zoom buttons to enlarge a section of the image to 5x or 10x, then use the D-pad to choose the area of the frame you want to see in detail.