Depth of Field is an important concept for photographers. How much of your photograph is going to be in focus? Is it a landscape scene where you want the viewer to see pretty much everything in focus, or is a portrait where you only want the subject to be in focus?
Depth of Field will determine how much of a photograph is in focus and which parts of the photograph will be out of focus. Here is a quick way to illustrate this in a visual way. Find a long fence or a series of many parking meters. Angle your camera to catch us much of the fence or parking meters as possible. Ideally you will have your camera on a tripod to keep each shot the same. Now, close the aperture way down to something like 22 or even 32 if you can and focus about half-way into the scene. Take the photograph. Now take a second shot with your aperture somewhere in the middle range like f/8 or f/11. Finally take a third shot with the aperture fully opened.
When you get back to your computer compare the three photographs. The depth of field should be the greatest in the first shot. That is, you should see more of the fence or parking meters in focus. In the third photo you should see the least depth of focus–just a small part of the fence or a parking meter or two in clear focus. Do you see the differences?
Now, this concept needs to be applied in the photographs you are creating with your camera in all different situations. Let’s say that you are shooting a baseball game. You only care about the player at the plate and the baseball, not the dugout or the fans in the background. So you will use a shallow depth of field by opening up your aperture as wide as possible. Be careful though, because if the baseball and the player are not fairly close together, only one will be in clear focus. Many sports photographers shoot at f/4 or even f/5.6 to try to get the best of both worlds–shallow depth of field, but not too shallow.
Let’s consider another scenario. Say you are on vacation and see this beautiful sunset that lights up the valley all the way up to an incredible mountain. The sun is behind you but the light is long and amazing. Your goal in this photo is to capture as much of the beautiful scenery as possible. This is where a deep depth of field can really help to keep as much of the scene in focus as possible. So you close down the aperture to f/22 or even more to capture this photograph.
Get the idea? Depth of field exists in every photograph to some degree. The goal is to get the proper depth of field for what you are trying to achieve. Practice and experiment with depth of field. You’ll be very glad you did when the photograph of a lifetime presents itself to you!