Focus Mode: Important Introduction
Understanding focus modes is key to getting the photo you want in a hurry – it’s the difference between in focus and out of focus results.
You’ve probably struggled to focus in the past and not been entirely sure why it just won’t lock on exactly what you want it to. Don’t fear, this post will tell you everything you need to make sure you never lose focus again.
One Shot / AF-S
This is the simplest of all of the focus modes and it does exactly what it says on the tin: focuses for one shot.
You would typically shoot on this mode with subject that’s not moving as the camera will only focus once when you depress the shutter button halfway.
This is the recommended mode when you want to use the camera’s focal lock to focus on the subject, then move the camera to recompose the frame. The camera will not focus again in this mode until you lift up the shutter button and depress it again.
AI Servo / AF-C
Photographers often refer to this to as continuous focus. It focuses when you partially depress the shutter but still monitors movement in the frame, making any necessary adjustments for you between the shots, without the need to remove your finger from the shutter button.
This mode is useful for shooting a moving subject, such as at a marathon or any other sporting event.
You would not be able to use the camera’s focal lock to recompose a shot in this mode; you’ll find that the camera continually tries to focus.
AI Focus / AF-A
This is probably the least understood mode and is actually a mixture of the two mentioned above.
When the camera has only slight movement, it will act as though it’s on One Shot / AF-S mode, allowing you to use the focal lock feature.
When the camera detects movement, the focus mode act instead like AI Servo / AF-C mode and track the subject.
This may sound like the best focus mode to use but I still tend to set mine to one of the other modes as I usually know what I’m shooting and what to expect. This mode does come in handy when you’re shooting still objects that are likely to move without much notice, such as a bird on a perch.
If you want to separate your focus from your shutter, you can learn more about back button focus here.