|Red-Shouldered Hawk (AI Focus AF)|
One Shot would work here until he decides to fly
One Shot (Canon)/AF-S (Nikon). This is the standard focusing mode photographers use most of the time. When you press the shutter half-way, the camera focuses one time and maintains that focus until you take a picture or take your finger off the shutter button. This mode is perfect for stationary subjects or subjects that are moving but not closer or farther away from you.
AI Servo (Canon)/AF-C (Nikon). With this focusing mode, when you press the shutter half way, the camera focuses continuously on the subject. It detects movement in areas covered by the focus points (either all of them or the ones you've selected) and tries to maintain focus of that subject as it moves. This is great for action and sports photography, especially when subjects are moving either toward you or away from you. It helps you maintain focus on your subject. The downside to this is that it will slightly lower the frame rate of you camera. You will be able to take fewer pictures per second.
AI Focus (Canon)/AF-A (Nikon). This is a hybrid mode of the first two. In this mode, the camera starts in One Shot/AF-S mode and will automatically switch to AI Focus/AF-A mode if it detects movement. This is ideal for stationary subjects that may move at any second, like birds. If you are shooting a Red-Shouldered Hawk perched on a branch, and he begins to fly, you don't want to take the time to switch autofocus modes.
|Red-Shouldered Hawk Taking Flight|
This is why I use AI-Focus AF for bird photography
|Immature Least Bittern, Manual Focus with 2x400mm lens|
Notes: Especially when manual focusing, make sure that your viewfinder's diopter is set properly for your eye. There's a diopter adjustment you can use to make sure that what you see through the viewfinder is sharp. Look for a dial next to your viewfinder.