Canon L lens

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Top-of-the-line Canon EF lenses are designated as L-lenses, or "Luxury" lenses. L-lenses have superior optical performance and are typically built with a solid construction to withstand constant use and harsh conditions. They can be recognized by a red ring around the front part of the lens. Most recent L lenses have sealing to help resist dust and water. L-lenses are usually reserved only for use by professionals and serious amateurs due to their high price and large mass.

Most L series lenses share a number of common characteristics:

Tough build, made to withstand the trials on the fields (some incorporating dust and moisture resistant rubber seals).
At least one fluorite or ultra-low dispersion glass element, combined with super-low dispersion glass and ground aspherical elements.
Non-rotating front elements, which are optimal for some filters (e.g. circular polarizers).
Relatively large apertures compared to other Canon lenses in the same focal lengths.
Where included, true ring-type USM (ultrasonic motor) and full-time manual focusing.

Note that there are some lenses which include one or more of these technologies yet which are not designated L-lenses. L-lenses are often equipped with USM and/or IS, but the optical performance is the key criteria.

Larger sized L-lenses, such as the 70-200mm and 100-400mm zooms and longer focal length primes (300mm+), usually have an off-white barrel (sometimes referred to as the color "putty") to reduce heat absorption under the sun that may otherwise affect the performance of the lens, as well as to identify Canon's lenses (for example at sporting events). However, shorter focal length L-lenses can be black (such as the Canon EF 24-70mm f/2.8L and all L-lens primes under 300mm, with the single exception being the 200mm f/1.8 - which has been discontinued.). Therefore L-lenses can be identified by either a lens barrel's off-white colour or, as on all L-lenses, the distinctive red ring on the lens barrel.