Zoom lenses are one of the most complicated types of lenses to manu facture. They exhibit a very variable focal length range. The difference to varifocal lenses is that you always obtain a sharply focused image when the lens is correctly adapted to the camera, regardless of the focal length. This is not possible with varifocal lenses as the sharpness (focus) always has to be reset when the focal length is changed. This type of lens is available as a manual or motorised version.