Fixed focus


Fixed focus

A fixed-focus lens is a lens of which the focus is not adjustable. The focus is set at the time of manufacture, and remains fixed. The focus is generally set so the depth of field ranges from one metre to infinity, which is acceptable for most cameras used for capturing images of humans. The lenses are usually therefore very slow.

Fixed focus can be considered an inexpensive alternative to autofocus, which requires electronics, moving parts, and power. Since a fixed focus lens requires no input from the operator, it is suitable for use in cameras designed to be inexpensive, or operate without electrical power.

Fixed-focus lenses are often used in disposable cameras, or low-end 35 mm film cameras. They also find use in webcams and mobile phones. Some mobile phones have a "macro" mode, which is essentially a second focus position of the lens.

Special-purpose cameras such as the Agiflite [cite web | url = http://photo.net/bboard/q-and-a-fetch-msg?msg_id=004pdu | title = Agiflite Aerial camera | work = Photo.net BBoard] are used for situations like aerial photography from aircraft. Because the ground is far from the camera, focus adjustment is not necessary. For 35 mm cameras, some superwide fixed-focus lenses have been made. [cite web | title = The Strange Case of the 12mm Fisheye | url = http://thesybersite.com/general/12mm-fisheye/index.htm | work = TheSyberSite ]

ee also

*Autofocus

References

External links

* [http://camerapedia.org/wiki/Fixed_focus Camerapedia - Fixed focus]


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