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What is AI-Servo and what should you use AI-Servo for?
AI-Servo is Canon’s name for continuous servo autofocus. AI-Servo on Nikon is called AF-C and AI-Servo on Sony is labeled continuous AF in the camera autofocus control menu or on a dial or switch on the camera. Despite the difference in the names, it all describes the same camera function.
Let’s dive a little deeper into this most useful camera feature.
What Is AI-Servo?
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So, exactly what is AI-Servo describing? Continuous servo autofocus, or AF, is describing that the focus confirmation is not tied in with or controlled by releasing the camera shutter, making it a different focusing mode from single-shot AF.
In single-shot AF modes, often listed on camera controls or menus as AF-S, the camera can only fire the shutter once there is focus confirmation from the AF part of the camera electronics. This is used with the thought of only capturing in focus shots of our subjects.
Single-shot AF works well as a default mode for general photography, since most of the time we just want our focus to be sharp in our images. The problem that comes up for using this mode is for moving subjects.
How to Use AI-Servo
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What is AI-Servo and how to use AI-Servo are actually linked questions. Looking back at single-shot AF, it only allows the release when the focus is confirmed. AI-Servo AF or continuous autofocus allows the shutter to be released regardless of focus confirmation.
This is an especially useful focus mode for action subjects or when we as the photographer are moving around a lot also. Sports and wildlife photography immediately come to mind but other genres of photography will benefit from this mode as well, such as weddings or other events, or even having a fun day taking pictures of kids, pets, and street photography.
Speaking of street photography, AI-Servo is also useful for many photojournalism situations. Basically, anytime either we or our subject is moving, single-shot AF can be somewhat problematic. So we switch to AI-Servo AF and trigger the shutter whether or not the camera AF sensor confirms sharp focus.
So It Takes Photos Out of Focus? No...
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This doesn’t mean that your camera’s AF isn’t making you take out of focus images. The AF is still working, it just isn’t linked to letting the shutter release. In fact, when you’re using your camera in AI-Servo mode, you can still see the AF continuously correcting between shots.
So, what is AI-Servo or continuous autofocus mode? It’s a focus mode for action photography that often results in more usable images of interesting moments when in these picture-taking situations.