What’s the difference between Canon AI Focus and AI Servo autofocus modes?
Asked 4/5/2011
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I’m using a Canon 60D and understand One Shot AF for subjects that stay still. I’m confused about when to use AI Focus versus AI Servo, and how they work in practice.
With AI Servo, do I keep the AF button or shutter half-pressed while following the moving subject so the camera keeps adjusting focus? Also, how is this different from panning?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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AI focus works like single shot but if the subject starts moving as you shoot the focus system will track the subject (so that it doesn't move out of the plane of focus). It's good for still subjects that may move unexpectedly.
AI servo continuously tracks the subject as long as you hold down the focus button and is good for continually moving subjects. For example if the subject is moving toward you the camera constantly measures the distance and adjusts the lens so that when you press the shutter the subject will be in focus (in theory, it can get it wrong).
The focus mode is separate to focus point selection, if you select a specific focus point that is the one the camera will use for all AF modes.
Finally I don't understand the last question, panning in a technique to move the camera to track a subject, not an autofocus mode. You should probably us AI servo when panning as you would expect the distance from the subject to camera to change as you pan.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
15y ago
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Generated from our catalog & community — verify before relying on it.
Yes. In AI Servo, you keep the focus engaged—typically by half-pressing the shutter or using a back-button focus setup—while you follow the subject. The camera continuously updates focus as long as focus is held, which makes it the right choice for subjects that are already moving or continuously changing distance.
AI Focus is more like an automatic switcher: it starts out like One Shot for a still subject, but if the camera detects that the subject begins to move, it switches to tracking behavior. It’s intended for subjects that may suddenly start moving.
One Shot is still best for subjects that are not moving.
A key point: AF mode and AF point selection are separate. The selected focus point is the point the camera uses, regardless of whether you choose One Shot, AI Focus, or AI Servo.
Panning is different: it’s a shooting technique where you move the camera to follow a moving subject, often to keep the subject relatively sharp while blurring the background. You can pan while using AI Servo, but panning itself is not an autofocus mode.
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