The level consists of an object lens assembly (11), motor driven focussing lens assembly (12) and a graticule (14) and creates an image on the graticule, the degree of sharpness of the image being detected and used to control the focussing motor (42). The motor drives the focussing assembly through a shaft which can be selectively coupled or decoupled either to the motor or a sharpness adjustment button (23) according to the axial movement of the button. The couplings can be provided to provide for both automatic an manual focussing. The coupling and decoupling operations can be determined by the axial direction in which the button moves.
