Back to basics: Focus Modes

Focus Modes

One Shot /AI Servo / Continuous Modes:

Beyond just the number of focus points a camera has, every digital SLR camera also includes several types of autofocus modes.

The two most common are called One Shot and AI Servo / Continuous autofocus.

 One shot mode:
•One shot autofocus is the mode to use for non-moving subjects.
•You press halfway down on the shutter release button, the camera picks an autofocus point to use, focuses and then (unless you've disabled it) beeps at you.
•If you want to change where the camera is focusing, you must release the shutter button, point the camera at something else, push halfway down on the shutter again and let the camera autofocus.
•This approach works great for landscape, portrait, macro or still-life work: anytime your subject is still and you have enough time to get accurate focus.

 

AI SERVO mode:

•For any subject in constant motion - continuous autofocus / AI SERVO is a blessing.
•In this mode, you press the shutter release button halfway down, the camera picks an autofocus point and focus is set.
•The big difference between this and one-shot mode is that if you continue to hold down the shutter button halfway, the camera will continue to adjust focus as your subject moves around the viewfinder.
•This is especially helpful if your subject is moving or even charging right at you.
•If you've got the camera on ONE SHOT AF mode, you will struggle get your subjects in focus when they are moving.
So how can we combat the above and make the best out of both functions? By using back button focussing.
Back to basics: Focus Modes
Back to basics: Focus Modes

What is back button focusing:

The camera usually focuses when the shutter button is pressed half way down, and then the photographer takes the picture when the button is pressed in fully.  Back button autofocus makes it so the shutter button doesn’t control the focus activation at all, but instead assigns another button on the back of the camera (hence the name) to activate focusing on the camera.

This means that you can leave your focusing mode on AI SERVO. If the subject is stationary, you can just press the back button to focus and let go when the focus is locked on your subject and if your subject decides to get up and move, just by simply holding down the back button, the camera will continuously focus as the subject moves.

It isn't always easy to adapt to using back button focussing and takes some getting used to but I can guarantee you that if you can get used to this change, it will make a massive difference to your photography.

Until next time,

Trevor

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