What do AF-S, AF-C, and AF-A autofocus modes mean, and when should I use them?
Asked 9/14/2011
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My Nikon DSLR offers AF-S, AF-C, and AF-A autofocus modes. What does each mode do, and which shooting situations are they best for? I’m looking for general guidance on when to use each mode rather than model-specific instructions.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
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AF-S is AF 'single'- your camera will focus on a fixed object when you press the AF button and will remain focused on that point for as long as you hold the button down. This is best for static subjects.
AF-C is AF 'continuous' - the camera will focus on whatever is in the relevant AF points (depending on how you have your AF coverage set up) and will attempt to keep the subject in focus wherever it moves, whether that's towards/away from the camera or laterally. This is best for continually-moving subjects, e.g. birds in flight.
AF-A is AF 'auto' and automatically switches between the two AF modes depending on what the subject is doing. This requires less effort on the part of the photographer, but you are relying on the camera guessing correctly what you are focussing on, and may result in unexpected focus.
For completion, on a Canon camera the equivalent modes are, respectively, One-Shot AF, AI Servo AF and AI Focus AF.
Originally by user456. Source · Licensed CC BY-SA 4.0
user456
14y ago
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Generated from our catalog & community — verify before relying on it.
AF-S means autofocus single. The camera focuses once when you activate autofocus, then locks focus at that distance as long as you keep it engaged. Use AF-S for subjects that are not moving, such as landscapes, portraits where the subject is holding still, or other static scenes.
AF-C means autofocus continuous. The camera keeps adjusting focus while autofocus is active, trying to track subject movement. Use AF-C for moving subjects, especially anything coming toward or away from you, such as sports, wildlife, or birds in flight.
AF-A means autofocus auto. The camera chooses between single and continuous autofocus based on whether it thinks the subject is moving. It can be convenient, but it depends on the camera correctly interpreting the scene, so it may not always pick the mode you want.
In practice: choose AF-S when you want focus to lock on a still subject, AF-C when you expect movement, and AF-A only if you want the camera to decide for you.
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