Macro and modular lenses
Macro lenses are specifically designed for small fields of view (FOV), which are approximately equal to the camera's sensor size. Macro lenses are specified in terms of their magnification relative to the camera sensor and are optimised for 'close-up' focusing.
Very good MTF characteristics and negligible distortion make them ideal for many vision applications. However, they lack flexibility, because it is not possible to change the iris or working distance. Special 'reverse rings' can be used on some standard or high resolution lenses, allowing them to be used as a macro lens.