Optical element used for transfer of scene to sensor. Compact digital cameras have unchangeable zoom objectives designed to work with specific sensor format. However to enable higher range to tele or wide area, some manufacturers provide use of tele and wide converter, nevertheless questionable usage. Changeable objectives are privilege used by SLR construction cameras, enabling us much more flexibility using camera because of large choice of different objective types. Unfortunately the price for that is huge bag on the back and higher cost. Changeable objectives are by construction divided on objectives of fixed focal point lenght and zoom objectives and by purpose on tele, normal or wide. Very important data about objective quality and purpose are showed by minimal F values (the smaller the F is objective is faster) and focal point lenght.
3 lens from Canon L series