Focal length
A term used in optics to describe the distance between the optical center of a lens and the point at which it focuses light. In photography, the focal length of a lens or zoom setting is a measurement that determines the magnification and angle of view of that lens or setting. Millimeters are the standard unit of measurement for it. However, because the precise focal length that must be used in order to produce a specific field of view is going to be determined by the size of the imaging chip that is utilized by the camera in question, its utility as a means of comparing different lenses is going to be reduced as a result of this fact.
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