Autofocus uses focus algorithms interpret the shooting scene and evaluate different aspects to determine which point should be in focus and thus can be handy. Previously we wrote about Auto Focus in Digital Photography and how to Avoid Blurry Photos in Digital Photography. In this article we will specially discuss about Autofocus as a tool to prevent blurry photographs.
Autofocus to Prevent Blurry Photos : Introduction
Before knowing the world of DSLR, it is common to take pictures that go blurry or the point of focus go wrong and you can not understand absolutely why. The main problem is the choice of focus modes which usually are entirely entrusted. Unfortunately, a camera is not smart enough to guess the best strategy to focus. So, on certain occasions, it may happen the result is fully unacceptable.
When we use the auto focus, as said at the beginning; the focus algorithms interpret the shooting scene and evaluate different aspects to determine which point should be in focus. Without going into the details of these algorithms, we can say that there are three elements that most influence them: intensity of the light, contrast and movement of the subject or camera.
Therefore, it is easy to imagine that in some situations the algorithms can be confused. For example, if you photograph a person in the shade or on a bright background, we could focus the background and the blurred person. Or, if we were photographing a still subject and the background were moving objects, the latter could be in focus at the expense of the subject. The DSLR cameras and bridge cameras, fortunately, give us the ability to have more control over how to focus. They also make multipoint focus available, which allow the photographer to select the point of focus using the dial on the camera’s back. The cheaper cameras have a dozen points for the focus, while the more expensive Professional allows you to select among fifty different points. If you want to learn to shoot with greater awareness, it is necessary to know how they work and when using different modes of auto focus.
Autofocus to Prevent Blurry Photos : How To Guide
Single-mode
In Nikon cameras, this mode is called AF-S, Canon in One Shot Focus. In this mode, the photographer chooses the point of focus from those available. Once the shutter button is pressed halfway, the focus is locked. But if your subject moves, you will need to focus again. This is the mode that allows more control to the photographer.
When to use: This mode is recommended whenever photograph is for still subjects: still lifes, portraits, landscapes, etc.. In these cases, the risk that the person moves is practically zero and be able to precisely control the point of focus may be necessary to make a proper photo. Conversely, if the person or persons are in motion, using this mode is likely to make us miss some opportunities to take pictures.
Continuous mode
In Nikon, this mode is referred to AF-C. In Canon it is called AI Servo. It allows you to select which point, among the available ones, must be focused on, one can correct the focus in the case the subject or the photographer will move. So, after we pressed the shutter button halfway, until you shoot, the camera can intervene to refocus adapting to changes in the scene.
When to use: This mode comes handy when we frame moving subjects like animals, children, athletes. Using this mode, we can change the angle in order to keep the focus point of your subject and the camera will continue to focus until it will press the shutter button all the way.
Automatic mode
In Nikon cameras, this mode is called AF-A, while in the Canon it is called AI Focus. You will probably find that the mode set the first time you turn on the camera, so that we will use it in our first photo. It automatically decides which of the above two modes are to use: if the subject is stationary, single-point mode, if the subject moves, the continuous mode.
When to use it: The automatic mode is not just for beginners. Thanks to the effectiveness of the internal algorithms of the camera, in most cases it makes the right choice. It may happen that we find ourselves in situations where the automatic mode fails and we get undesirable results. In this case, can we evaluate which of the two modes are to use.
