From the course: Learning Your Nikon DSLR Camera

Understanding focus points and autofocus

From the course: Learning Your Nikon DSLR Camera

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Understanding focus points and autofocus

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- When you look out onto a scene, your eyes need to focus. Now typically, your brain chooses one place to focus, and a camera really works the same way. The auto-focus mechanism can really only focus at one particular distance in a scene. Now if this is working properly, the point should line up with your subject. Your camera includes a number of different focus points. The exact number is going to vary by model. Typically, more expensive or newer cameras include more auto-focus points than earlier generations. Ideally, the camera's going to look for one of these points and make sure that it overlaps with the subject. However, the process isn't always perfect. Sometimes you'll need to override this automatic mechanism and choose the focus point manually to force the camera to focus on a particular place. To change the different modes you have a few different options. First up, you're going to press the auto-focus button at the bottom of the camera here. It's a switch that goes between manual and auto-focus, and as you switch that there you'll see that the auto-focus methods are indicated right there. Now if I press this button, I can actually change how it's going to focus. And, you see here we can choose between different options of auto, servo, and continuous. Now, make sure that the focus selector lock is set into the auto-focus position. And if we press this here, we can actually turn the dial to change the methods. So notice that we have different methods depending upon the camera. Right now it's looking in a larger zone, and a smaller zone, or all the way down to a single spot method. Now as you change these different methods, most folks are going to go with an auto-selection method, and perhaps auto-focus in an automatic mode. This is going to give you the most flexibility when first starting out. However, we do have other controls that allow us to actually change what's in focus so it really dictates based upon your shooting style. If we invoke the live view mode, you're going to see things a little bit differently. In this case, we have a single point here, this red dot, and you can actually move that around on the subject. So if I set that dot on the background when I engage focus, you'll see that the backdrop is in focus and that point turns green. If we move that point down to our subject here, and, we set our focus, you see that now it turns green, and it is the piece of fruit that was used for the overall focus. Now, think of it this way, it's really up to you which method is used. Single point auto-focus is going to use a single point. Make sure though that this switch here is not locked. On the back of the camera you have a little dial. And, it is possible to actually lock the auto-focus. In this case this disables auto-focus, and if we try to move that, you see that the command dial has no effect. So make sure that that dial is in the unlocked position, like such, so you can actually adjust it. Now, this can be quite useful for a stationary subject. That single point allows you to set it on the subject, and it works pretty well. The dynamic area auto-focus is going to let you set the initial point, but then it's going to select surrounding pixels. Remember, this is going to go off of that letter D. Let's go ahead and exit live view. If I press that button there, and I switch from single, S, over to a dynamic mode, you see that we can have different numbers of points depending upon the system that's in play. The larger the number, the more potential points that are going to be used. So for example, if I set this to D9, it's going to use nine points to automatically determine the focus. And that usually works well for something that's relatively stationary. However, if I increase this, we can go ahead to a higher number, 21 points or 39 points. This is going to work better for something that's moving a lot, for example soccer players. Now the 39 point method is generally useful if something is moving a lot and erratically, something like birds. There's also a method called 3D tracking. And this is great if something is moving from side to side. In this case the camera is going to track the subject, but really leave the focus set to the same general distance and it makes small changes. It will allow the camera to automatically follow the subject and try to adjust. So this can be accessed, let's just press that button on the side, and you see the 3D method. Now do keep in mind that the exact methods that you have are going to vary from camera to camera. More expensive camera bodies are going to have more options. But, in general, it works pretty well. The live view method is the simplest, so if that's how you're used to shooting, that's fine. Particularly, those of you that are migrating from something like a cell phone. But you will get much better performance if you rely on the optical view finder and take advantage of some of the additional auto-focus modes.

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