Varifocal lens

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This article is about varifocal camera lenses. For corrective eyeglass lenses, see Progressive lens.

A varifocal lens is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes, as compared to parfocal ("true") zoom lens, which remains in focus as the lens zooms (focal length and magnification change). Many so-called "zoom" lenses, particularly in the case of fixed lens cameras, are actually varifocal lenses.[1]

A varifocal lens. Left image is at 2.8mm, in focus. Middle image is at 12mm with the focus left alone from 2.8mm. Right image is at 12mm refocused. The close knob is focal length and the far knob is focus.
A varifocal lens. Left image is at 2.8mm, in focus. Middle image is at 12mm with the focus left alone from 2.8mm. Right image is at 12mm refocused. The close knob is focal length and the far knob is focus.

[edit] References

  1. ^ Cavanagh, Roger (2003-05-29). Parfrocal Lenses. Retrieved on 2007-11-18.
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