A zoom lens, including: a first lens unit and a second lens unit, in which the first lens unit includes: a first lens sub unit which does not move; a second lens sub unit which moves for focusing; and a third lens sub unit which does not move; and in which the following expression is satisfied, \u22122. A current consumption of the video display monitors is measured at a sampling rate. Oxidation is performed to form thicker or thinner oxide portions on the exposed portions of the first and second structures relative to unexposed portions of the first and second structures. In addition, the complete client program cannot be executed without involving the server. The movable plate has first, second, third, and fourth positions where a switch actuator in the first group is in alignment with a truncate slot so that the aligned switch actuator can be thrown and where all other switch actuators in the first group cannot be thrown.