Canon EOS Prime (Fixed) Lenses – Comparision and Reviews

Canon EF-S Lenses = were specifically designed for Digital SLRs with APS-C sized imagers (not full frame). These include: Digital Rebels XT, XTi, XS, XSi, T1i, T2i, T3i and Canon EOS 7d, 20d, 30d, 40d, 50d and 60d. SLRs with APS-C size imagers have a conversion factor of 1.6 applied to the lens focal length.

APS-C Imager = This imager is smaller than a Full Frame imager. Lenses used on SLRs with APS-C imagers have a focal length about 1.6x that of full frame imagers. This means that the telephoto end of the lens will be greater. New digital lenses have been developed for these type of SLRs.
Full Frame Imager = This means that the imaging sensor is the same size as 35mm film. 35mm lenses will operate on these DSLRs with the same focal lengths as they do on 35mm film cameras.
IS = This denotes that this lens has built-in image stabilization to negate vibration and camera shake that can make pictures blurry. This is especially important with telephoto lenses where camera shake is magnified.
USM = This lens has an Ultrasonic Motor – This is a special type of motor within a modern autofocus canon lens that allows for extremely quick focus shifts with very little sound. (Non USM lenses can be slow and noisy).
Canon L Lens = If you see a capital “L” in the lens description (such as f4L, f4 L, f/2.8L for example) it signifies that this lens is part of the L Series which incorporates superior lens construction and USM for quiet, high-speed autofocusing. These are superior lenses.