Focal length
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The focal length of an optical system is a measure of how strongly the system converges or diverges light; it has units of length, and for an idealized thin lens is equal to the distance between the l
Sketch of human eye showing rear focal length f′ and EFL
28 mm lens
50 mm lens
70 mm lens
Focus (optics)
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In geometrical optics, a focus, also called an image point, is a point where light rays originating from a point on an object converge. Although the focus is conceptually a point, physically the focus
Focal length
…strongly the system converges or diverges light; it has units of length, and for an idealized thin lens is equal to the distance between the lens and its focal points. A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light. A system with…
A demonstration of camera focus on different distances, showing a bamboo rooftop
Text on a page that is partially in focus, but mostly not in varying degrees