Considering the depth of field factor

Learning depth of field and how to control it is one of the single most important aspects of photography. This is what separates you from the point-and-shoot crowd, and this is what allows you to control the exposure rather than allowing the camera to do it. One of the first steps in becoming a serious photographer is to get that camera out of full Auto mode and learn to use DOF. Here are several important concepts to remember:

  • The smaller the aperture, the deeper the DOF (the other two factors remaining the same). For example, if the lens focal length and the shooting distance stay the same, the DOF is much deeper at f/16 than at f/1.4.
  • The shorter the focal length of the lens, the deeper the DOF (the other two factors remaining the same). For example, comparing a 28mm lens with a 50mm lens at the same aperture and shooting distance, the DOF is deeper with the 28mm lens.
  • The greater the shooting distance, the deeper the DOF (the other two factors remaining the same). For example, if the same subject is photographed from 10 feet and then from 20 feet away, the zone of sharpness in the foreground and background is greater at 20 feet.
  • Your Canon dSLR features a Depth of Field preview button that can help you see what you’re about to shoot. When you focus through the viewfinder, you’re not necessarily seeing the image you’re going to get, in terms of DOF. This button lets you see the DOF as it will be shot. Pressing the DOF button stops-down the aperture to the f-stop you set, so that you can see the depth of the image you’re about to shoot. Although a 50mm lens may provide the crop factor of an 80mm lens, for example, the DOF remains the same. This is why you might hear or read that photographers insist DOF is different with digital: They are judging DOF by the effective focal length of a lens rather than by the actual focal length.

ARTISTIC CONSIDERATIONS

Depth-of-field can range from a fraction of an inch to infinity. For example, a close-up of a person’s face may have shallow DOF with some of the background blurred — a common technique in portrait photography. In a mountain landscape, you want a deep DOF, with both the foreground and background in focus. The same is true of a group portrait, such as a high school football team with players tiered in bleachers, where you want all the players’ faces sharply focused. In a close-up still photograph, such as in a product photo, you might employ a very shallow DOF to isolate the subject from a distracting background. The amount of DOF is an important creative treatment that can be used to emphasize drama in composition, isolating a subject from its surroundings.

Category: Photography System

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