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What is Focal Length
Posted By: Ole, 01-31-2009, 06:23 PM

A lens' focal length is a measure of how strongly it bends the light. A photographic lens (convex lens) will bend parallel light rays so that they all intersect in the same point, the focal point. The focal length f of the lens is defined as the distance from the optical center of the lens to the focal point.

The focal length is thus a characteristic of the lens only and not related to sensor size/film format or what camera the lens is mounted on. A 50mm lens is a 50mm lens is a 50mm lens.

The Field of View (FoV) of a lens, on the other hand, depends on the sensor size/film format.


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Last edited by Ole; 02-01-2009 at 12:16 PM.
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05-15-2009, 10:34 AM   #2
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focal length is very important to photographers, it gives you the idea of distance
05-15-2009, 12:20 PM   #3
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This seems very basic. How to determine the focal point and optical center, especially of the wide angle lens?
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