Reversing cameras can either use wide-angle or fisheye lenses. A wide angle lens projects a much large image circle than a standard design.
Wide-angle lenses can magnify the subject more if necessary. There are two varieties of wide-angle kens for reversing cameras – short-focus and retrofocus.
Short-focus lenses have multiple glass elements. As the focal length decreases, the distance of the rear element of the lens from the sensor also decreases.
Retrofocus, on the other hand, have an asymmetrical design, allowing the rear glass to be further away from the film plane.
As well as reversing cameras, wide angle lenses are found on mobile cctv systems.