Many home users and indeed some amateur photographers conflate the notion of telephoto and zoom lenses. Truth be told, telephoto lenses are designed to give a slim angle of view. Measured against the common 35mm standard, telephoto lenses focus at a distance, generally between 70 and 100 mm. Advanced Canon telephotos can create super narrow apertures and get great resolution at a 600 mm focal length or greater.

You can also get a zoom lens standard with many Canon digitals, such as the S2 PowerShot, the SD-500 PowerShot, and the Rebel XT. Zooms give you the option to vary your focal lengths, so you can catch so-called wide-angle shots--those with a shorter focal length then your camera's aperture--as well as long distance telephoto shots. Of course, an all-purpose zoom may not have sufficient coverage or clarity for detailed photographic purposes.

The good news is that Canon now offers dozens of lens choices, ranging from cheap plastic throwaway lenses to $7,000 works of art that come fully-equipped with internal gyroscopes and anti-noise USM controls. True Canon camera buffs tend to accumulate a slew of lenses over time. Indeed, one of the ways that Canon ensures that customers stay with the brand is to introduce new and exciting lenses on a regular basis.

A very good Canon telephoto lenses is the EF 24 to 85 mm 3.5-4.5 IS USM lens, which offers detailed manual focus control. You can get great telephoto and semi telephoto control with this piece of equipment as well. If you only want to purchase a single Canon lens, you might go with the 28 by 135 mm IS. You get image stabilization as well as a range of focal options.