Overview

This is the longest telephoto lens among Canon's lineup, and a terrific choice for any long-distance application-outdoor sports, wildlife, news photojournalism, and so on. - Canon EF 800mm f/5.6L IS USM Lens 

• It's actually lighter than Canon's EF 600mm f/4L IS lens, weighing just under 10 lbs.
• It uses a refined optical design, with two fluorite lens elements, one UD element, and one Super-UD-glass element, for outstanding correction of color fringing and superb contrast and sharpness.
• This super-telephoto lens uses magnesium-alloy barrel construction to enhance its light weight, and has weather-resistant gaskets throughout for use in harsh conditions.
• It's compatible with both the EF 1.4x II and 2x II tele extenders for even more reach: EOS cameras with 45 AF points will continue to provide autofocus at the center AF point when the lens is used with the 1.4x extender.
• Finally, it's image stabilized, providing up to 4 stops of correction for camera shake. This makes it even more practical in many situations.

Features:

• The image stabilizer gives the equivalent effect of a shutter speed four stops faster. The lens also has a second image stabilizer mode that is optimized for following shots of moving subjects
• The lens features outstanding image quality through the use of fluorite, super UD and UD lens elements
• Ultrasonic motor (USM) for quick and quiet autofocusing
• Manual focusing is available after the subject comes into focus in autofocus mode (ONE SHOT AF)
• The AF Stop button for stopping the AF operation at anytime
• Focus preset enables you to focus instantly at a preset distance
• A truly round aperture hole results in a nicer background blur
• The lens is compatible with Extender EF1.4X II and EF2X II
• Tight seal structure ensures excellent dustproof and drip-proof performance
• Designed for lighter weight with parts made of magnesium alloy