EF 20mm f2.8 USM
The EF 20mm f2.8 USM fills a gap between the EF 14mm f2.8 and the EF 24mm f2.8. In the past, a 20mm lens was regarded as a special optic, but the ever-expanding focal length range of wide-zoom lenses means that the EF 200mm is seen as a general-use, super-wide angle lens.
The lens uses an ultra-sonic motor (USM) for silent, high speed focusing. The 20mm lens is able to focus from infinity to its closest shooting distance of 0.25m in 0.3 sec.
Manual focusing is possible at any time while in the AF mode - a wide rubber focusing ring makes focusing easy.
The EF 20mm lens uses a rear focusing system similar to that of the EF 24mm f2.8 lens. This ensures a sharp, hgih-contrast performance at all focusing distances. Rear focusing also means that the hood and filter attachment at the front of the lens does not rotate, making the use of polarising and special effects filters much easier. The overall length of the lens remains the same at all focus settings.
Focal length and maximum aperture: 20mm f/2.8