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 a 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] which give lens designers more flexibility in optical design trade-offs (focal length range, maximum aperture, size, weight, cost) than parfocal zoom. These are practical because of autofocus, and because the camera processor can automatically adjust the lens to keep it in focus while changing focal length ("zooming") making it suitable for still photography where a change in magnification of the subject, as demonstrated below is not a problem. The change in the subject size is a significant problem in video and true parfocal designs are needed for higher quality video work. Varifocal lenses can be used for image display as well as capture, and Meta's Reality Labs has confirmed developing a varifocal display for virtual reality.[2]
A varifocal lens. Left image is at 2.8 mm, in focus. Middle image is at 12 mm with the focus left alone from 2.8 mm. Right image is at 12 mm refocused. The close knob is focal length and the far knob is focus.
^Cavanagh, Roger (2003-05-29). "Parfocal Lenses". Archived from the original on 2007-10-07. Retrieved 2007-11-18.
^"Introducing the Team Behind Half Dome—Facebook Reality Labs' Varifocal Prototype".
A varifocallens is a camera lens with variable focal length in which focus changes as focal length (and magnification) changes, as compared to a parfocal...
Zoomar lens introduced in 1959 was the first varifocallens in regular production for still 35mm photography. The first modern film zoom lens, the Pan-Cinor...
distance. This lens type has two segment lines, dividing the three different correcting segments. Progressive addition or varifocallenses provide a smooth...
barrel of the lens assembly. In early varifocallenslenses, the focus also shifted as the lens focal length was changed. Varifocallenses are also used...
compose the image. Many zoom lenses, particularly in the case of fixed-lens cameras, are actually varifocallenses, which gives lens designers more flexibility...
the commercial Zoomar lens, including the use of optical compensation. Back applied for a patent in 1946 for a "Varifocallens for cameras", which described...
Frank G. Back, Reflex Camera VarifocalLens. United States Patent #2,902,901; granted 8 September 1959. Ray, Photographic Lens. pp 172-173. Stephen Gandy...
macro, the 28-210mm/4.0-5.6 and the 3.8-5.6 varifocal zoom, and the 28-85mm/2.8-3.8 varifocal macro zoom lenses were praised in contemporary reviews of the...
function in MF only. Whether it is single or varifocal depends on the optical characteristic of the lens. **Although the adapter itself cannot have a...
16OPF1-2M-01 zoom lens with a focal length range of 12–120 mm and a wide-angle lens of 10 mm. The other configuration included a 16OPF12-1s varifocallens and a 0...
classified as fixed, varifocal, or pan–tilt–zoom (PTZ camera). Fixed cameras feature an immobile perspective on the subject, whereas varifocal cameras have the...
advert with Virgil Tracy and the Hood to promote its new "Reaction" varifocallenses. This featured a jetpack chase between Virgil and the Hood over mountainous...
model was brought out. In reaction to the upcoming use of heavier varifocal or zoom lenses and the bigger synchronous electric motors attached to the body...
is a candidate member of the class of swept-volume 3D displays is the varifocal mirror architecture. One of the first references to this type of system...
need reading glasses, and also those who have started to need bifocal or varifocal spectacle correction due to ageing changes in the eye. It can be used...
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