Abstract: To improve the accuracy and the speed of an autofocus method, using which a present best focal plane (13) may be found in an automated manner, which enables a best possible image quality for an object (3), which is located at a specific working distance (11) to an optical imaging system (1), it is provided that at least one parameter used during a z-scan (17) be adapted in an automated manner as a function of a presently set optical zoom level and/or a current estimated value of the working distance (11). During the z-scan (17), a present location of a focal plane (12) of the optical imaging system (1) is displaced within a scanning range (14) along an optical z-axis (8) of the imaging system (1), wherein the individual focal planes (12) are each evaluated to identify the best focal plane (13) among them.