“Depth of Field” is probably one of the most overlooked and, possibly, misunderstood concepts for the beginning photographer.
Webster’s Dictionary defines it as: the range of distances of the object in front of an image-forming device (as a camera lens) measured along the axis of the device throughout which the image has acceptable sharpness. Pretty simple, huh? Simply put it is the distance in front of and in back of your subject that appears to be in focus. That takes care of the “what”, now for the “why”.
Depth of field is one of the most important concepts to understand; the most important is light without which there is no photography. Have you ever seen a photograph where the background looks like an abstract painting? What about a photograph where everything seems to be in razor sharp focus? If you answered “yes” to either of these questions you have experienced depth of field. Now you see why you need to master this, right?
There are a number of factors that affect depth of field with aperture, focal length and subject distance being the ones I will discuss here. The general rule is that the smaller the aperture, the more depth of field you achieve and this is true if focal length and subject distance are constant. You also get increased depth by using a wide-angle lens as opposed to a telephoto lens.
Depth of field is also tied to “hyperfocal distance” – this is the point in which everything behind your subject (think “to infinity and beyond”) is in focus. You could think if it as the “sweet spot” wherein you achieve maximum depth of field. It used to be easy to estimate the achieved depth in the old days of film cameras because it was shown right on the lens. There were markings on the barrel that indicated the depth range at any focal length, all you had to do was look! Today you have autofocus lenses and all of the settings are done through the camera so the manufacturers took this information off many of the lenses.
I have some examples that I think will emphasize the importance of depth of field in your everyday shooting. All of the pencil photos used in this post were shot with a Nikon D60 at a focal length of 55mm with the lens focused on the first pencil.
The first photo is an example of shallow depth of field and was shot at f/5.6. You can see that the first pencil is sharp, the second a little softer and the focus drops off a little with each pencil. 
The next photo was shot at f/16.
The final image was shot at f/36 and you can see that a lot more of the image is sharp. For each image the lens was focused on the first pencil.
Now, onto a new example.
The first photo is an example of shallow depth of field and was shot at f/5.6.
The next photo was shot at f/16. Notice that the leaf in the foreground is still prominent in the image but the background is a little sharper and you can begin to tell what the background is.
The third and final image was shot at f/36. This is not a great photograph. The background is much sharper and you have a hard time discerning it from the leaf in the foreground – it is just a mess.
All of the photos of the leaf were shot with a Canon T3i and a Canon 18-135mm f/4-5.6 lens with a focal length of 120mm.
Now that you have mastered the concept of depth of field – go out and shoot! Set up a tripod, pick your subject and shoot it with every aperture you have available. Do the same with different focal lengths. What have you got to lose? The worst that can happen is that you shoot 100 images, get 1 great shot and have to spend a couple hours outside. I can think of worse things, can’t you?
Read Joe’s blog: Exploring Photography with Joe Valencia. Learn more about Joe here.
All photos by Joe Valencia. Follow him on Instagram.
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