I get it. Depth of field is fun to play with and makes our pictures look amazing, but I'm here to say that more of a good thing is not always better.
Look at the image featured on this page of my beautiful wife, Emily. The depth-of-field adds to this image to make her stand off the page; however, this image suffers from too shallow depth of field. The depth of field was only about two inches in this picture because I used an aperture of f/1.8, a 50mm lens, and I was only two or three feet away from the subject. You can see that part of her face is out of the plane of focus, and that is a bit distracting. What I really wanted was to make her completely in focus and just blur out the background. You might not be able to tell this on the small preview of the image, but it's obvious if you click to make it big. This post is for those of you who always crank the aperture down to the lowest number available.
Controlling depth of field tip #1: Remember that aperture is not the only factor that controls depth of field. If you are physically close to your subject and are using a long lens, this will drastically decrease the depth of field. Remembering this will be a reminder that you might have to use a slightly higher aperture in this situation so that the depth of field isn't too shallow.
Controlling depth of field tip #2: Don't let depth of field look like a mistake. We all know you didn't INTENTIONALLY blur part of the face. It was an accident. Show enough care for your photos to watch out for these mistakes.
Controlling depth of field tip #3: Carefully monitor the hairs that often stick up toward the back of someone's head. This is one of the easiest ways to tell if your depth of field is too shallow. Look on the LCD at the hairs toward the top of the head to see if they are in sharp focus.
Controlling depth of field tip #4: Zoom in to 100% on your LCD. If you aren't sure if the depth of field is too shallow on a portrait, zoom all the way in on a photo you've just taken and check problem areas like the nose, hairs on the top of the head, etc.
Controlling depth of field tip #5: If you want the background to be extremely blurry while still getting the entire model in perfectly sharp focus, just have the model take a few steps forward. Separation between the model and the background will make that background appear much creamier.
Have you noticed this problem in your own photos? Does this even matter? Sound off in a comment below. I'd love to know your thoughts.