Constant maximum f/4 aperture Robust L series build Fluorite and UD elements The Canon EF 70-200mm f/4.0L USM is perfect for the demanding amateur or semi-professional, boasting a telephoto focal length, robust build and quick aperture. Either high-end APS-C or full frame models, such as the EOS 5D, are best suited to this lens and sports and wildlife photography are the most compatible genres. Although the aperture is not as bright, this lens is far cheaper than the f/2.8 aperture version and much lighter, making it an excellent choice for most situations. The L series construction grants the Canon EF 70-200mm f/4.0L USM protection against moisture and dust entering the body. This makes the lens capable of standing up to a day out in the field, regardless of the conditions. The constant maximum f/4 aperture is selectable regardless of the focal length, improving the low light performance by allowing a large amount of light on both the imaging and autofocus sensor even if only a limited amount is available. The Ultrasonic Motor further improves the focus speed, keeping it rapid as well as virtually silent, and the Fluorite and UD elements reduce aberrations that can compromise the clarity and sharpness of your images.