Photography

Basic Photography Lessons - Depth Of Field (DOF)

Depth Of Field (DOF) refers to the range of distance from the camera at which the objects will appear to be in acceptable focus. Anything outside this range will start to appear blurred. An extreme case where the DOF is very small is in Macro Photography such as in the picture of a grasshopper shown here. In the middle portion of the picture there is an area where the eye is very sharply focused while the images away from this point and those that are closer appear blurred.

In reality, the lens can only focus precisely on one particular point. Anything that falls beyond or before that point will be out of focus and will appear blurred. The degree of blurring however does not become obvious or discernible right away due to the limitation of the sensor's resolution or the size and quality of the viewing media. To a certain degree the DOF is influenced by the the image resolution and for prints, the size and resolution of the printed material.

A small depth of field is useful for portraits where the subject is placed within the focused range while the background is rendered blurred. This gives more emphasis on the subject and a dramatic distortion on the background. Landscape pictures on the other hand will benefit more with a large depth of field as you would need all the objects within the scene to be as clear as possible.

Depth of Field is influenced basically by two factors, the distance of the subject to the camera, and the aperture opening. The farther the subject is from the camera the bigger the depth of field becomes. The nearer you are to the subject on the other hand makes the depth of field smaller. This is one difficulty usually encountered in macro photography as the subjects are usually very near the camera that the depth of field are often measured in millimeters and focusing becomes very difficult. It is usually compensated by changing the Aperture opening. A larger aperture opening (lower value) reduces the depth of field while a smaller opening (higher value) increases the depth of field. Although the effect of the aperture value to the depth of field is not so dramatic but the results can be quite significant.