Canon EOS Lens Features (Vocabulary)

Canon EF 300mm Lens
Canon EF 300mm f/2.8L IS USM

Lens Features for Canon Lenses

When you look at the names of lenses, you find weird combinations of letters and numbers that are not normally part of the English language unless you are part of the photographic community. Here are the letters you may come across and the meanings for those letters.

F-stop – Aperture. This is the size of the opening of the camera lens when a photo is snapped. Usually given as a number with a decimal, such as f2.8. The lower the number, the wider the aperture. So a lens with an aperture of f2.8 will have a wider opening than a lens with an aperture of f4.0. The F-stop is always given as the widest possible aperture for that particular lens.

L - Contains Aspherical Elements. A premium line of optical glass suited for demanding professional photographers and artistic purposes

IS – Image Stabilization. A gyroscopic stabilizer built into the lens which compensates for camera shake in order to achieve sharp photos. With IS it is possible to take good quality shots with 2-4 stops slower shutter speeds than possible without IS.

USM – Ultrasonic Motor. Lenses with the USM designation feature faster and quieter focusing operations.

EF - Electro-focus. Through a series of electronic contacts, the control of lens focusing is provided by the camera body.

EFS – Electro-focus (Short). A slightly different EF mount that is compatible with digital slr cameras that employ a “crop sensor”, also designated as APS-C sensors.  Cameras that qualify for EFS lens mounts are: Canon Digital Rebel, XT, XTi, XS, XSi, T1i, T2i, 20D, 30D, 40D, 50D, 60D, and 7D.

DO – An alternative approach to lens formulation that yields compact telephoto lenses and decreased chromatic and spherical aberrations.

Macro - Macro is a special lens that has been specifically formulated to get up close to objects to give higher magnification and focus at very close distances.