Specifications:

Brand Canon
Focal Length 400mm
Aperture Maximum: f/4
Minimum: f/32
Camera Mount Type Canon EF
Format Compatibility 35mm Film / Full-Frame Digital Sensor
Angle of View 6° 10′
Minimum Focus Distance 10.83′ (3.3 m)
Magnification 0.13x
Optical Design 18 Elements in 12 Groups
Diaphragm Blades 9, Rounded
Image Stabilization Yes
Autofocus Yes
Tripod Collar Yes Fixed – rotating
Filter Thread Drop-In: 52 mm
Dimensions (DxL) Approx. 5.04 x 9.16″ (128 x 232.7 mm)
Weight 4.63 lb (2.1 kg)
Package Weight 7 kg
Box Dimensions (LxWxH) 19.0 x 16.0 x 14.0″

Features:

Super telephoto 400mm f/4 lens is compatible with full-frame EF-mount DSLR cameras, as well as APS-C-sized sensors where it will provide a 640mm equivalent focal length.

Gapless dual-layer diffractive optics contribute to a marked reduction in chromatic and spherical aberrations as well as benefit the design of a relatively compact and lightweight lens.

One large diameter ground aspherical element and one ultra-low dispersion UD element minimize aberrations and distortions while also contributing to greater sharpness and clarity.

A Sub Wavelength Coating has been applied to individual elements to control lens flare and ghosting for greater contrast and color fidelity when working in strong lighting conditions.

An Optical Image Stabilizer helps to minimize the appearance of camera shake by up to four shutter speed stops to better enable working in low-light conditions and with slower shutter speeds. Three distinct IS modes are available:
standard single-shot mode, a panning-optimized mode, and a mode that only activates the Image Stabilizer during the exposure.

A ring-type Ultrasonic Motor (USM), along with optimized focusing algorithms and a high-speed CPU, is employed to deliver fast, precise, and quiet autofocus performance as well as full-time manual focus override.
Focus Preset function is available to quickly recall a programmed focusing position.

Focus Limiter switch lets you constrain the focusing to three different ranges to suit different applications: 10.8-26.2′, 10.8′-infinity, or 26.2′-infinity.

A Power Focus setting is available, and allows you to electronically and smoothly adjust your focus position to suit video recording. This setting utilizes a dedicated ring in front of the main focusing ring and allows you to use one of two different focusing speeds.

A weather-resistant design protects the lens from dust and moisture to enable its use in inclement conditions. Additionally, fluorine coatings have also been applied to the front and rear lens elements for further protection against fingerprints and smudging.