Get Into Focus
If you’re not using manual focus, it’s a good idea to become familiar with how your camera decides to focus so the subjects you want are sharp. If you’re in the wrong mode, your camera may be confused about what you want to focus on (face it, it will never really know what is important to you 100% of the time) and pick the wrong subject.
Cameras today have three basic focus modes: Auto Single Shot, Auto Continuous and Full Manual focus. Your camera may have one or more of these modes.
- Auto Single Shot means your camera will find a something to focus on, lock on it when the shutter release is pressed halfway down and then stay there until the shutter is tripped. Some call this AF-S or Single Shot.
- Auto Continuous will keep picking focus points based on the assumption that your subject is moving and needs to be tracked. It will keep a moving subject in focus. Some call this AF-C or AI Servo.
- Full Manual is all about you!
Smartphone Note: Your phone’s camera will use continuous focus until it locks on something.
Here’s the experiment you can run:
1) Grab your instruction manual because camera’s vary too much for me to explain them all here. Flip to the section on focus modes.
2) Learn how to switch between them.
3) Change your camera to Auto – Single Shot. This may show as AF-S, Single Shot or the like.
4) Set your camera to Program Mode as we’re not concerned about exposure control right now. Zoom out to 50mm.
5) Pick a single object in the room about six feet away. Point your camera at it and press the shutter down halfway. Your camera may beep and it will lock focus on the object.
6) With your finger still on the shutter, half pressed, move the camera to a very near object (your hand?). Notice that the focus does not change and your camera will take a photo of the out of focus hand if you tell it to.
7) Now switch to Auto – Continuous mode. This is AF-C or AI Servo on many cameras.
8) Point the camera at an object in the room about six feet away. Press the shutter down halfway.
9) The object will come into focus. Now, with the shutter still half pressed, point the camera to a closer object, maybe 2 feet away.
Do you notice a difference at this point?
There is a big difference between these modes! If you are trying to recompose a picture after locking focus on one object, but have your camera on AF-C, if will keep changing focus on you! This is not what you want.
Likewise, if you are using Single Shot and tracking a moving object coming at you and press the shutter down halfway, then a fraction of a second later press it all the way down, the object could have moved from that point of focus on which your camera was locked.
Continuous focus modes are getting more and more advanced. Most DSLRs have settings for this mode that allow you to choose to track a subject or to keep picking new subjects as they come into frame
When To Use Each Mode
- Stationary objects
- When you want to focus on one item, and then recompose your shot without losing focus
- Cars on a race track
- Anytime the camera focus messes up
- Night shots
- Low light with not much contrast (your camera needs contrast to focus)
- When you just want to
NOTE: Some camera, like Canon cameras, have another mode called AI Focus, which attempts to know if you want Single Shot or AI Servo. Sometimes it works and sometimes it doesn’t.
Yesterday’s Experiment was: Learn The ISO Limits Of Your Camera
Tomorrow’s Experiment is: Depth Of Field – Changing Aperture
Questions? Pop ’em like Pez in the comments section below. or email me at firstname.lastname@example.org.
Photography Basics – A 43 Day Adventure, and its companion 40 Photography Experiments, are series written by professional photographer Peter West Carey. The series are designed to unravel the mysteries of photography, helping you can take better pictures. Subscribe here to receive all the updates and bonus material. Your comments are always welcome.
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