There are generally three focusing modes, at least, on my Rebel there are three to consider.
First, you have One-Shot focus. which means you focus on your subject and the focus doesn’t change, it stays at the focal distance it was set to.
Second, is Al Focus auto focus, which will focus on your subject, but if the subject moves the focus setting will change to Al Servo auto focus.
Third, Al Servo Auto Focus will get focused on your subject and then follow and change the focal distance every time something moves. This could be a good thing or a bad thing.
If you’re shooting portraits or still subjects you’ll want the one-shot auto focus, since it will focus on what you want and stay focused on it. If you’re afraid your subject is going to try to move real soon, may not stay put, you’ll want the Al Focus for just in case. if you’re photographing birds or other wild animals that are moving you’ll want to use Al Servo auto focus, since this will cause th focus to follow your subject.
When NOT to use Al Servo: when you’re doing portraits or still subjects. some sensors are so sensitive that the slightest movement will cause it to be out of focus, since it will be trying to follow the movement. if you want sharp images of landscapes or people you do NOT want this to happen.
I typically shoot in One-Shot auto focus, as it also requires less power from your battery, thus reducing the risk of having to charge or replace batteries on the go. And it works for most things i shoot. I do People, Landscapes, Birds and other wildlife, special events, you name it! but i always use One-Shot focusing because I know it will focus on what I want it to focus and the focal distance will not change. Shooting entirely in One-Shot will take some practice, especially if you’re shooting wildlife, because you’ll want to focus just ahead of where your subject will be in a moment, so as to capture the moment as soon as it’s at the focus point.
I hope these tips are helpful to all of you who read this article.
This is Sarah’s Scenes Real Life Photographer.
Lesson: watch the focus, be creative, but really think about your options. just because it sounds right at one moment doesn’t mean it will be right for you the next.