A zoom lens is a mechanical assembly of lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed focal length (FFL) lens. A true zoom lens, also called a parfocal lens, is one that maintains focus when its focal length changes. A lens that loses focus during zooming is more properly called a varifocal lens. A zoom lens is a key feature on a digital camera as it adds tremendous flexibility to your photography. Here is what you need to know about them. Most compact digital camera have optical zoom lenses; that's lens that can vary its field of view in order to magnify ('zoom in') or broaden ('zoom out') a scene. These are ideal for when you cannot get close to your subject or want to include more of it in the shot, making the camera very versatile. Focal Lengths: Zoom digital cameras have their focal lengths (the range through which the optics in a lens can move) specified by comparison with the focal length of the familiar ('35mm') film camera. They are indicated on the camera lens in millimetres. Whilst this may sound confusingly technical, helpfully all you need to know is simplified in the descriptions of digital cameras by using terms such as 'two times' (abbreviated to '2x') or four times ('4x') and so on and so forth. The wider the focal range, the greater the 'x' factor (or 'times' factor) becomes and the greater the apparent magnification. Here is an example to make all this clear. A digital camera with a zoom lens which has a 35-105mm focal range is said to be a '3x' optical zoom lens, because the highest focal length figure is three times the lower focal length, i.e. 35 x 3 =105. A 28 - 112mm lens would be a '4x', for example, and so on and so forth. The optical zoom range available to digital cameras is growing as lens technology improves and there are now many digital cameras with so called 'ultra-zoom' ranges with up to 12x optical zooms, offering a focal range of round 35mm to 420mm! The most common digital cameras have 2x or 3x zoom lenses, and while they can't zoom as much as an 'ultra', they are less expensive and just as much fun to use. Optical Zoom or Digital Zoom? Digital cameras, almost without exception and including those that already have an optical zoom lens, have a feature called digital zoom. This can electronically enlarge a portion of the sensor's image to produce a zooming effect. Optical zoom works by using the lens to magnify the scene and it utilises the entire sensor area for the image, retaining full image quality and resolution. Digital zoom enlarges a small, central portion of the sensor instead. Therefore, it will produce blocky, grainy images and should be avoided if top quality prints are required. Remember, buying a digital camera with an optical zoom lens will give you great flexibility in your shot taking, and the larger the zoom range, the greater the flexibility you will have.