 BetterPhoto Member |
Short Focal Length What does "short focal length" mean?
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Jon Close |
The focal length of a lens is the distance between the film and the optical center of the lens when the lens is focused on infinity. Focal length determines the angle of view of the lens. Short focal lengths give a wide angle of view. The shorter the focal length, the wider the viewing angle. In 35mm film cameras a lens of 14mm or 15mm will have a wide 114-180 degree viewing angle. 24mm gives about 84 degrees, 28mm corresponds to 75 degrees, and 35mm is about 63 degrees. "Normal" focal length lenses (50mm) have an angle of view approximately equal to that of the human eye, about 45 degrees. Long focal length lenses (85mm and longer) are telephotos and give a narrow angle of view, seemingly bringing distant objects closer.
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John A. Lind |
The angles of view Jon gave for various focal lengths are across the diagonal of the film frame, between opposing corners (it's called the diagonal angle of view). They are not the horizontal angle of view. Using the diagonal is the universally accepted method for stating a lens angle of view. If you see an angles of view for lenses in books, specifications or advertising, you can assume it is the diagonal one unless stated otherwise. -- John
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