Focus Mode Basics
Pretty much all modern digital cameras have different focus modes that can be changed based on the type of shot you are trying to get. Obviously, focusing on a stationary subject (something that will not move at all), or a person (who may move slightly) or a goose flying over a lake or a kid’s basketball game, will all require a different way of setting up your focus mode. So, the way it works is that when you are taking a picture of something that won’t move you lock focus and take your shot. When you have a subject that is or will be moving, you will then need your camera to adjust and readjust focus as you try to get a good shot. This is where the focus modes come into play.
Single Area Focus
Let first look at Single Area AF. You choose one focus point in your viewfinder and your camera looks for contrast only in that one single focus point. You then acquire focus by half pressing your shutter button (or pressing the back button focus if you’ve set that up), and focus is locked on the scene for your shot. This mode is known as One Shot AF on Canon cameras and AF-S on Nikon Cameras. Other DSLR brands such as Sony, Fujifilm or Pentaxall all have the same functionality even though the menu designations may vary.
Continuous / AI Servo Focus
This is the mode that you would select if you have a moving subject. Things like pets running, sports, etc. can be tracked with this type of focusing method. It’s really interesting the way that this works. Essentially it predicts where a moving subject will be when you take your picture and focuses at that point, automatically readjusting focus as the subject moves as you continue pressing the focus button. This mode is called AI Servo on Canon and AF-C on Nikon. Other DSLR brands such as Sony, Fujifilm or Pentaxall all have the same functionality even though the menu designations may vary.
Some DSLRs include another focus mode that will automatically switch between Single Area Focus and Continuous/AI Servo focus. With this setting the camera will lock single area focus if it determines that the subject is stationary and will switch to continuous focus if it detects that the subject is moving. Canon cameras that have this call it AI Focus and on a Nikon camera it is designated AF-A. Other DSLR brands such as Sony, Fujifilm or Pentaxall all have the same functionality even though the menu designations may vary.
Most modern DSLRs have good video recording quality and a fairly advanced focus mode that is specific to video. These are full-time servo AF modes and they show up in your Live View when you shoot a video. On my Canon EOS 80D I have something called dual pixel tracking focus which works excellent for tracking focus on slightly moving subjects. It doesn’t track really fast-moving subjects all that great, however. I know that Nikon also has this feature on many models and call it AF-F. Other DSLR brands with video capability will generally have the same functionality even though the menu designations may vary.
Learn to Change the Focus Modes on Your Camera
You can see that it’s important to be able to choose the right focus mode the capture the picture you want. Check out your camera manual or watch some YouTube videos to see how to switch between the various focus modes on your camera.
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