by Jim McGee

The Digital Rebel is the first Canon digital SLR to support a new lens mount called the EF-S. The “S” stands for short back focus. An EF-S lens has the same contacts as a standard EF lens but the rear element sits further back into the camera body, bringing it closer to the image sensor. EF-S format lenses will also reduce the size of the image circle that is projected onto the sensor.

The 1.6x factor when used with Canon’s EF 35mm lenses doesn’t represent a magnification of the image provided by the lens. But rather represents a cropping of the available image (see What’s the Big Deal About a Full-Size Chip? for a complete explanation).

By reducing the size of the projected image Canon can design smaller, lighter lenses using smaller elements than can be used for either 35mm or for the 1Ds which has a full frame chip.

The first such lens is the EF-S 18-55mm f3.5-5.6. This lens provides the equivalent coverage of a 28-90mm lens in 35mm format. It offers a circular aperture for smooth out of focus elements, internal focus, an aspherical lens element, and a minimum focus distance of just 0.9 ft (0.28m).

Another interesting feature of this lens is a new optical coating that Canon claims to minimize ghost images and flare when used with digital imaging sensors. It is compatible with extension tube EF 12II & EF 25II but it is not compatible with any of Canon’s previous or current digital cameras other than the Rebel.

Sorry 10D owners.

This lens will be available packaged in a kit with the Rebel for $999. Separate pricing for this lens is not yet available.