The Canon EF 70-200mm f/2.8L USM lens is a telephoto zoom lens for Canon EOS cameras. The inner focusing system and USM (ultrasonic motor) gives you faster, more precise auto focusing. Regardless of whether you're in manual or auto focus mode, the full-time focusing ring always works. This means you can auto focus on a subject, but manually change the focus by turning the focusing ring. The EF 70-200mm f/2.8L USM lens is compatible with optional Canon extenders. The aperture value and focal lengths with the extenders are as follows:

EF1.4x II:                       f/4, 98-280mm
EF2x II:                          f/5.6, 140-400mm
Focal Length/Aperture:      70-200 mm f/2.8
Lens Construction:           18 elements in 15 groups (including 4 UD-glass elements)
Maximum Aperture:          f/2.8 (constant)
Minimum Aperture:           f/32
Angle of View:
                                       Diagonal: 34° - 12°
                                       Vertical: 19°30' - 7°
                                       Horizontal: 29° - 10°
Min Focus Distance:         4.9' (1.5m)
Dimensions:
                                        Diameter: 3.323"
Length:                            7.848" (8.593" with caps)
Weight:                            45.29 ounces