Description by canon:

A high-performance telephoto zoom lens. The EF 70-200mm 1:4 L USM delivers excellent image quality in a varierty of situations. Its compact, lightweight design make it an excellent travel companion.

• L-series optics
• Light and compact
• Constant f/4 maximum aperture
• Fluorite and UD lens elements
• Fast autofocus
• Super Spectra coatings
• Circular aperture for pleasing background blur

A lightweight, compact telezoom delivering professional performance and accomplished handling.

L-series quality
The L-series is Canon's flagship professional lens range, representing the best in precision-designed EF optics. L-series lenses combine superior performance with superlative handling, and are resistant to dust and moisture.

Professional features
A maximum aperture of f/4 is available at all focal-length settings, ensuring shutter speeds do not change as the lens is zoomed. A non-rotating front element simplifies the use of filters, such as polarisers and grads.

Ultrasonic focusing
A ring-type ultrasonic motor drives autofocus extremely quickly, and in near silence. Excellent holding torque ensures the point of focus is reached accurately, without overshooting. Furthermore, full-time manual override is available, making it possible to adjust focus without leaving AF mode.

Super Spectra coating
Super Spectra coatings ensure accurate colour balance and enhance contrast. They also reduce flare and ghosting – a common problem caused by light bouncing off a camera's sensor.