Tutorial: Lenses

Lens motors

Every EF, EF-S and EF-M lens has a built-in focusing motor. This moves the lens elements in response to the autofocusing commands from the camera body.

Many recent EF and EF-S lenses use an ultrasonic motor (USM) which are quiet and offer fast autofocusing. Some recent lenses use stepper motor technology (STM). Lenses with STM focusing generate even less noise, making them particularly useful when shooting video with EOS cameras – the microphone is less likely to pick up any noise from the lens.

Image stabilisation
Image stabilisation detects camera shake using two gyro sensors in the lens. These measure both the angle and speed of the movement and instruct a special group of elements within the lens to move at right angles to the lens axis. The amount and direction of this movement counteracts the amount and direction of the camera movement. Learn more here.

America's Cup, © Matteo Chinellato 2012, Canon EOS 7D

The result is that the image on the sensor does not move, despite the camera movement. Canon’s image stabilisation copes with situations from simple camera shake to the vibrations of a moving vehicle, boat or even a helicopter.

The latest models offer a four-stop advantage, allowing you to get a similar result with IS at 1/15 second as you would get at 1/250 second without IS.

L-series lenses
Canon has created a very special group of EF lenses – the L-series. These lenses – which can be identified by a red ring around the lens barrel – are designed to meet the needs of professional photographers. L-series lenses are manufactured using the very latest techniques in lens technology. They include lens elements made from fluorite crystal and ultra-low dispersion (UD) glass to help eliminate problems such as chromatic aberrations.

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