Depth of Field


I have discovered a new phenomenon with the advent of Digital Photography. As I’m shooting my portrait shots people will walk over and want to see a particular picture of themselves or a loved one. When they look at my shots they tend to ask, “I have the exact same shot; why does yours look so much better?” The difference is almost always the same thing: an incredibly deep depth-of-field. As I look at their shots I can see everything into the great unknown in sharp detail.  The problem with having your entire scene in focus like this is that your viewers won’t quickly know what the subject of your portrait is. Landscape photography is the only reason that you’d really want to have long-depth-of-field (i.e. having that flower in the foreground in focus as well as the mountain behind). So here are a couple helpful hints on how to control your depth-of-field and make your portraits look more professional.

1. Aperture: All Digital SLR cameras have the ability to adjust your aperture. Aperture is measured in what’s known as “stops”. Stops are measured in increments of 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, etc. The lower the number on the aperture, the shallower the depth-of-field will be. Most consumer lenses will have what’s called a “variable aperture” ranging from 4-5.6 which means the aperture will change as you zoom the lens. The more zoomed-in you are the higher the aperture will go. To make sure that you are shooting on the lowest aperture possible, change the shooting mode on your camera to “Aperture Priority.” It’s usually the one on the wheel labeled “A”. This will put the camera in a mode where everything will be automatic except for the aperture. This means that you will still have the advantages of automatic light recognition, without the aperture changing in the middle of your shots. So in short, the lower the number the aperture is set at, the shallower the depth-of-field.

2. Zoom: There are two types of lenses: zoom lenses and prime lenses. A prime lens is a lens with a fixed-focal-length (no zoom) while a zoom lens has a variable-focal-length (zoom). When you “zoom in” on your subject you are compressing the background of your scene, compressing the depth-of-field. This will cause your depth of field to become shallower. So if you are taking a portrait and you want to “blur” out the background, try taking your zoom lens, backing away from your subject, zooming in and taking the shot. This will allow your backgrounds to compress and create a soft background for your subject.

There are other ways to control your depth-of-field such as hyper focusing/lens babies/etc., but none of these are simple techniques that you can carry into your everyday shooting. Aperture and Zoom are just the simple techniques that professionals use to achieve a professional look to our photos.

I’d love to know what you think about this post, or hear if you have more questions. Feel free to leave your questions in the comments. If there is a subject you’d like me to cover or a camera accessory you’d like to have reviewed, let me know.