Using Aperture: Creative Power with Your Camera’s F-Stop

If you’ve owned an SLR (single lens reflex) camera for a while and have yet to take it off the “auto” setting, you’re missing a tool that will allow for creative shooting and control over your final image: the aperture setting, also known as “f-stop.”

To understand the potential behind its use, you first need to understand what is meant by “depth of field,” which is affected by your choice of aperture. Depth of field refers to the area in a photo that is in sharp focus. This area can be increased or decreased by careful aperture selection when you make your exposure.

How do you know whether your chosen aperture will give you a shallow or long depth of field? The numbers tell the story. If the number is large, the depth of field will be long. If the number is small, you’ll have a shallow area of focus. An aperture setting of f/22 will provide a sharper overall image than one of f/4.

Aperture for Creative Control
On most SLR cameras, there are two ways to adjust aperture to your advantage. One method is to use the setting usually labeled “Av”, which stands for aperture value. This setting will allow you to select the f-stop that suits your needs best. Consequently, the shutter speed will adjust to slower or faster as needed to obtain a good exposure. If stopping action is not important for your subject, this is probably the easiest and most reliable way to experiment with the possibilities of aperture for photo composition.

The other way to control for aperture is to use the full manual setting usually labeled “M”. This setting allows you to choose both your shutter speed and the aperture, achieving a balance between shutter speed and depth of field that best suits your shooting needs. Your camera guide can give you specific details about each setting on your exposure control dial.

Aperture Cleans up the Clutter
Have you ever taken photos of your children at play, thinking they’d be incredible glimpses of their personalities, only to look at your print and see the clutter and mess in the room instead? You can begin to make use of the power of the f-stop when you’re taking those candids at home. This is a job for the wide open f-stop, a setting of f/4 or so. By opening up your aperture to its widest, the effect is that of shallow depth of field, throwing everything into soft focus, except for your subject. The clutter is still there, but will have a soft focus and detract less from your intended subject, the happy faces of your children.

Take a look at the two examples shown here. One was shot with a small f/stop of 32, the other with a wide open f/stop of 4.0. You can see how this simple tool right on your camera can replace weekly housework, at least in your photos!

Tip: If you are taking photos of family, friends or pets with a wide-open aperture, make sure their eyes are your point of focus. As long as the eyes are clearly focused, any softness about the edges will be largely unnoticed.

Aperture Brings It All into Focus
On the other end of the spectrum, there are situations in which you will want the greatest depth of field available. Any type of subject that requires sharp detail throughout would fall into this category, such as landscapes or cityscapes. Don’t think of this as a tool for just scenery, however. If you have an athlete in the house, a larger depth of focus will insure that the greatest area of the playing field is in focus. This is important, because the action moves so quickly across the field at any given time. If only one portion of the field is in focus when you snap the photo, the subject may not be within the focus area if you have a small depth of field. (When photographing sports or fast-moving subjects, shutter speed will often be the more important variable to consider when freezing action.)

Regardless of the depth of field, every image has a focus point where the final image is the sharpest and clearest. When focusing on your subject, keep in mind the point at which you want your sharpest focus and use that as your focusing point (such as a person’s eyes). Study the examples shown here. The first set was shot with a shallow depth of field at an f-stop of 5.0. Each picture uses a different focus point. The second set of photographs was shot with a larger depth of field at an f-stop of 22, again using different focus points. You can see here the difference your focusing point and depth of field can make on the final image.

A Few More Tips and an Aperture Trick
Keep in mind that the lens choice also has an effect on the aperture and the resulting depth of field. A telephoto lens compresses the image, so that things that appear close together in your image are really much further apart. The opposite is true for a wide angle lens.

If you use the macro setting—the little flower on the dial—it will result in a very shallow depth of field. Although this can be an advantage in shooting close-ups of things like flowers, you need to accept that part of the image will have a bit of soft focus. A trick I learned for this type of shooting involves using the telephoto lens instead. If you can step back far enough to zoom in on your intended subject with a wide aperture of f/5.6 or larger, you can isolate your subject, blur the background and still have a crisp image. The wildflower photo was shot in this manner, allowing sharper focus of the entire plant.

Try It Yourself
If you’ve been telling yourself to explore your camera’s full potential, shooting on the Av setting is a great place to start. Open up the lens or stop it down to achieve the amount of focus you need to best show off your subject’s charms. An excellent resource for those wanting to know more about exposure control as a creative tool is the book Understanding Exposure: How To Shoot Great Photographs, by Bryan Peterson.