Depth of field refers to how much of your picture is in focus. Since pictures are only two dimensional, we can make them appear more realistic by adding some depth to our photos. By using the smallest number f-stop (like f/16 or f/22), we create the greatest sense of depth in our photos. This is because at these settings, most of our photo will be in focus.
For example, photograph a subject that is far in the distance, and include something near you (like a tree or a tree branch). Use the branch as a framing device, and set your camera at the smallest f/stop that you can. Set your focus on infinity. If you have a depth of field preview button on your camera, use it and see what is in focus.
Everything from the tree branch to the mountain in the background should be in focus. To get the most depth possible in your photos, set the infinity symbol opposite whatever f/stop setting you are using. For example, if you set your f/stop at f/16, turn your focusing ring until the infinity symbol is directly opposite f/16. This is called hyperfocal distance, and it will maximize how much of your photo is in focus. Try it out and see for yourself.
On the opposite end of depth of field, you may only want a very small portion of the photo to be in focus. If this is the case, use a large number setting for your f/stop, and you will get a very limited section of your photo to be in sharp focus. This is good for focusing attention on a single element in your photo, and will throw the rest of the photo out of focus.
Be careful if you are using this technique on people, though. If you take a portrait at f/3.5, for example, focus sharply on the eyes, as the depth of field is so small at this setting that parts of the face may become out of focus. But it is better for the face to be slightly out of focus than the eyes, unless that is the effect you are going for.
Once again, experiment with your camera and different settings and see what you like and dislike. You are the photographer and you have the final say. You’ll only get better at taking photos, by shooting a lot of pictures and practicing with various techniques and lighting situations. Until we meet again…