A fisheye camera is a camera that uses an extremely wide-angle lens to capture a viewing range of about 180 degrees. This type of camera is called a “fish eye” because it approximates the vision of a fish’s convex eye. The lens produces curvilinear images of a large area, while distorting the perspective and angles of objects in the image.
There are two types of fisheye cameras, and they produce different angles of view, different types of distortion, and different photo shapes. Full-frame lenses capture an image that is usually 180 degrees from corner to corner, while the vertical and horizontal angles are smaller. These images fill the rectangular film frame. Circular lenses generally capture a 180 degree view of the horizontal, vertical, and diagonal angles. Images captured by circular lenses are round or oval inside the film frame and the frame around the image is black.
Focal lengths of fisheye lenses depend on the format of the camera. Using 35 mm film format, a circular image will typically have a focal length of 8-10 mm, while a full-frame image will have a 15-16 mm focal length. Newer lenses have been created with focal lengths in the 4.6-6 mm range. Digital single-lens reflex (SLR) cameras in 1/4 inch or 1/3 inch format can have a focal length of 1-2 mm.
The fisheye camera was first developed for scientific use, to record astronomical features of the full sky and to take forest canopy images for analysis. One benefit of the ultra wide-angle lens is the ability to photograph a large view from a limited space. For this reason, miniature fisheye lenses are valuable in security and commercial cameras, as they can record activity over a wide area from a single vantage point. IMAX movies also use a fisheye camera to capture panoramic shots and project the movies on a dome-like screen.
Photographers also use the distortion and wide angle benefits of these lenses to make interesting and unusual images. A landscape photograph taken by a fisheye camera will show a pronounced curve of the earth. Subjects close to the camera will have large, distorted features, while the focal length makes subjects at a distance look abnormally small. On a camera with a 180-185 degree view, two photos taken from exactly opposite directions can be digitally stitched together to make a complete 360 degree image. Due to these interesting image-making possibilities, the fisheye camera has become a popular gadget.