Image stabilisers help to prevent blur caused by movement of the camera, such as by shakey hands. The stabiliser is especially useful when shooting in low-light conditions.
Lens speed (f), indicates how much light the lens is capable of shooting to render the subject. It is the ratio of the diameter of the aperture input and focal length.
Unwanted noise is evident in the photographs as grain or bright colored stains. Noise most often occurs when shooting in low light conditions.
USM (UltraSonic Motor) is a lens sharpening system characterized by Canon. This drive uses piezoelectric micromotor to autofocus on subjects.
Focusing on the subject determines the sharpness of the final image. To properly focus, you need to choose a focal plane that is parallel to the sensor. Everything that passes through the focal plane will then be in focus.
