About a Fisheye Lens

A fisheye lens is an extremely wide-angle camera lens. This wide angle results in a curved image that represents subjects from a very broad field of vision. Fisheye lenses have a number of scientific and aesthetic applications.

Development

Fisheye lenses were originally designed for use in photographing clouds. By capturing a wider stretch of the sky than would be possible with a traditional lens, meteorologists were able to pull more useful information from a single image.
Fisheye lenses developed alongside other lens types during the early days of photography in the mid- to late 19th century. The fisheye came to represent the extreme on the wide-angle side of the spectrum, with telephoto lenses at the opposite end.
Because of its degree of distortion, fisheye lenses have been used only in a limited way. Their inclusion in standard lens kits is rare, and their applications in motion picture cameras is also very infrequent.

Optics

Like any compound camera lens, a fisheye lens uses a series of convex and concave elements to bend light entering the lens and project it onto the film frame. Fisheye lenses come in a variety of styles. The differences among them are mostly due to different focal lengths. The construction of a fisheye lens places it in one of two major categories; circular (producing a circular image in the center of the film frame) or full frame (in which the image is enlarged enough to cover the film frame entirely, turning it into a rectangle).
The mapping function of a fisheye lens refers to the degree of distortion which, consequently, determined how much of the surrounding space will be represented in the final image,.

Evolution

The first fisheye lenses were of the circular variety, capturing a 180-degree field of view and representing it as a circle in the center of the film frame. During printing, corresponding lenses could be used to un-distort the image captured with a fisheye lens, generally for use in scientific applications.
Full-frame fisheye lenses were derived from circular models once demand rose and camera manufacturers saw that there was a market for fisheye lenses among amateur and professional photographers. Nikon produced the first full-frame fisheye lens in the 1960s.

Additional Scientific Applications

Fisheye lenses are especially popular among scientists studying certain natural ecosystems. The process of hemispherical photography involves placing a camera with a fisheye lens among a growth of trees, pointing upwards, toward the sky. An image produced from this angle shows how much of the sky is effectively blocked out by the trees, and a series of images taken over time can be used to chart how those trees grow and their effect on solar radiation.
Hemispherical IMAX theaters use a fisheye lens in the film projector to create an image that fits their curved screens. Other optical devices, such as security camers and common peepholes, use fisheye lenses to offer a wide range of view from a fixed location.

Other Uses

Fisheye lenses are used by photographers to achieve a number of unique optical effects. Landscape photographers often prefer to use fisheye lenses because of the curvature they produce in an image of the distant horizon, which may suggest the vast scale of the space.
Other photographers use fisheye lenses to distort familiar objects, bringing a degree of abstraction to what might otherwise be a banal subject. A fisheye lens may also allow a photographer to get very close to his subject while keeping the entire subject in frame.

Resources

• Lens Types Explained