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P H O T O G R A P H Y C O N T E S T Sponsored by A.J. Hirsch |
Serge
Richmond Hill High School
First Place
2007 OAPT 4U Photo Contest
Aperture and Depth of Field
The main difference between the two photographs is that the background is in focus in the first photograph, but out of focus in the second. The apple remains in focus in both photographs. This effect was achieved by manipulating the image’s depth of field. The depth of field is the distance from the subject in which objects are in focus. The subject, in this case the apple, was always in focus, but the trees in the background were only in focus in the first photograph. This is because in the first photograph, the depth of field was large enough to include the trees and other background objects, but in the second it was so small that it only allowed objects within several centimetres of the apple to be in focus. The depth of field was controlled by varying the lens aperture, which is the size of the opening that determines how much light is admitted into the lens. A small aperture, f/22.0, was used to create a narrow, but long depth of field in the first photograph. In the second, a larger aperture of f/3.5 was used to ensure that the depth of field was small enough that only the apple would be in focus. To ensure that the same amount of light passed through the opening in both photographs, the shutter speed was made slower (1/3 sec) in the first photograph and faster (1/125 sec) in the second photograph to compensate for the change in aperture.