Canon L series lenses have a red ring around the lens barrel.
For photographers with a full frame sensor camera like the Canon 5D Mk II, or for those using cropped sensor cameras who want even greater telephoto zoom in a lens, the super telephoto range, generally a lens that covers a range of 400 mm or greater, is an excellent choice for wildlife photography and demanding scenes where the photographer cannot get close to the subject. Canon's L series EF 100-400 mm is one such lens, while Sigma goes even further with telephoto distance and wide angle, offering a 50-500 mm.
Mounts
Both the Canon EF 100-400 and Sigma 50-500 work with Canon's EF lens mount, meaning that they are compatible with all Canon cameras. They are designed for full frame cameras like the Canon 5D Mk II, which have a sensor the same size as 35 mm film. When used on an EF-S mount camera, such as the Rebel XSi, the lens will have a 1.6 crop factor, changing the focal length on the Canon 100-400 to 160 to 640 mm, and the focal length on the Sigma 50-500 to 80 to 800 mm.
Focusing
The Canon 100-400 mm has an ultrasonic motor built in for faster, quieter focusing. The Canon is a push/pull lens, meaning that you have to manually move the lens forward or backward on the barrel to adjust the focal length. The Sigma 50-500 has a standard ring focal length adjustment. The minimum focusing distance of the Canon is 5.9 feet/1.8 meters. The Sigma 50-500 has a hypersonic focusing motor, the Sigma answer to the Canon USM, and has a variable minimum focusing distance of 1.64 to 5.9 feet/.5 to 1.8 meters, depending on the focal length used.
Weatherproof
The Canon 100-400 is one of Canon's L series of lenses, a lens series that designates its highest level of quality. As part of that line, Canon weatherproofs the L series lenses like the 100-400 by adding a rubber ring on the mount connection to eliminate the potential gap between the lens and camera mount. The zoom ring, zoom extension and switch panels are also weatherproofed, so that you can shoot in dusty and even rainy conditions knowing that your lens is secure. The Sigma lenses are not rated as weatherproof.
Construction
The Canon 100-400 has 17 lens elements in 14 groups, including a fluorite lens element and a Super-UD (ultra-low dispersion) lens element to eliminate chromatic aberrations and create a lens with a accurate transmission of infrared and ultraviolet light. The Canon measures 3.6 by 7.4 inches/92 by 189 millimeters and weighs 3.1 lbs/1,380 grams. The Sigma lens has 22 lens elements in six groups, including four SLD (special low dispersion) glass elements for accurate color and exceptional sharpness. The Sigma measures 4.1 by 8.6 inches/104.4 by 219 millimeters and weighs 4.34 lbs./1970 grams.
Accessories
Both the Canon 100-400 and Sigma 50-500 come with tripod-mount collars on the lens, so that you can mount the lens to a tripod instead of the camera, providing better balance. If you shoot with multiple camera bodies you can also switch bodies while leaving the lens mounted. The Canon takes 77 mm filters. The Sigma takes 95 mm filters, which are harder to find. The Sigma comes with a step-down filter ring to change the 95 to 86 mm, but Sigma recommends not using a polarizer filter on the lens, as you may not be able to take it back off. The Canon's 77 mm filter size is compatible with polarizers.
Tags: Canon 100-400, focal length, Sigma 50-500, Canon series, series lenses, 100-400 Sigma, 100-400 Sigma 50-500