Lenses
Other than the image sensor, the lens is the part of the camera that has the greatest effect on the quality of your images.

Focal length
One of the most important characteristics of any lens is its focal length. It's the focal length that determines a lens' angle of view-wide angle, normal, or telephoto.

Lens focal lengths are indicated in millimeters (mm). On a more familiar 35mm camera, a lens with a focal length of less than 35 mm is considered a "short" or wide angle lens and one over 65mm is considered a "long" or telephoto lens. Lenses between 35mm and 65mm are considered normal and the 50mm lens is the most common normal lens.

Angle of view
describes how much of a scene the lens "sees". A short lens has a wide angle of view; as the focal length gets longer, the angle of view becomes narrower. A short lens will capture a wide expanse of a scene; a long lens with its narrower angle of view will isolate small portions of the scene without your having to move the camera closer to the subject.

Magnification
is related to the lens' angle of view. Since a short lens includes a wide sweep of the scene, all of the objects in the scene are reduced to fit onto the image sensor. Long lenses have a much narrower angle of view, so objects in a scene appear larger.

Digital cameras use the same relationships as other cameras to determine wide-angle, normal, and telephoto lenses. However, the focal lengths are much shorter because solid-state image sensors are much smaller than the smallest film. For example, while 35mm has an area of 36 x 24 mm, a 2/3-inch image sensor is only 8.8 by 6.6 mm and many sensors are even smaller.

Zoom lenses
Many digital cameras come with zoom lenses that let you change the focal length of the lens on the fly. The range of focal lengths a zoom lens covers is usually specified by its magnification. A 3X zoom lens will enlarge or reduce the subject in an image by three times depending on which way it's zoomed over its full range. The equivalent range when used on a 35 mm camera is also usually given, for example, "38mm ~ 114mm."

Zoom lenses come in two varieties; optical and digital zooms. An optical zoom lens actually changes the amount of the scene falling on the image sensor. Every pixel in the image contains unique data so the final photo is sharp and clear. A digital zoom lens uses sleight of hand by taking a part of the normal image falling on the sensor and then saving that part as is, or enlarging it to fill the sensor. It does this by adding new pixels to the image using interpolation.

The interpolated image doesn't have as many unique pixels as one taken with an optical zoom so is inferior. In fact, you don't even need this zoom feature because you can get exactly the same effect just by cropping a normal image in a photo-editing program and then enlarging it.

Although many zoom lenses work by pressing buttons or a zoom lever, some cameras have zoom rings on the lens just like those on zoom lenses for 35mm cameras. By turning the zoom ring during an exposure, you can get special effects, especially when combined with flash.