Fisheye lenses - photography in the round


It is possible to construct lenses with shorter focal lengths and wider angles of view than even the super wides. These lenses are known as fisheyes, probably because of their bulging, hemispherical front elements. Angles of view are often greater than 180 degrees, and images are circular instead of rectangular.


Fish eyes has very short focal length (as little as 6mm) and it creates a circle small enough so that all of it is contained within the sensor. A fisheye lens does strange things with straight lines. Unlike most lenses, which are corrected for as many optical defects as possible, a fisheye is deliberately uncorrected for barrel distortion. Straight lines, from the center of the image outward, are bent more and more until they match the curvature of the circle at its outer limits. The result is a peculiarly warped circular image with a tremendous angle of view. With a fisheye lens you must take care that your own feet (or tripod legs) do not appear in the picture even when the camera is level and pointed straight ahead.


Some fisheyes are made in longer focal lengths (up to about 17mm) and so throw larger circles. The result is rectangular rather than circular images, as with more common place lenses. However, even though a complete circle cannot be seen and the angle of view is somewhat smaller, most of the characteristically curved lines are still visible. Lenses of this type are known as full frame fisheyes or semi fisheyes.


In the 14mm to 17mm range lenses that cover the full frame can be either fisheye or rectilinear (reproducing straight lines as straight). However, even with identical focal lengths these differently constructed lenses create quite different results.


In view of their limited use and high cost (especially in the shorter focal lengths), fisheyes lenses are not often purchased. However, one or two manufacturers have tried to make the fisheye more popular and available by supplying it in the form of an auxiliary lens to be attached to a prime lens and used in combination. Although this method brings down the cost of a fisheye, it also reduces convenience, lens speed and optical performance. If a fisheye lens is one you must have, you will undoubtedly be better satisfied with a prime lens rather than an "add on" substitute.

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More about telephotos lenses

- Shorter wide angle lenses
- Moderate wide angle lenses
- super wide angle lenses
- tips about using wide angle lenses
- tips about using fisheye lenses

 


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