An automatic exposure (AE) sensor includes a line-selecting circuit for line selection between horizontal lines and vertical lines, in addition to components of a typical AE sensor. The line-selecting circuit temporally filters a SYNC pulse for notifying a subsequent circuit about a pulse timing of an imaging signal to select a line to be read out and to cause the subsequent circuit to change an active pixel region. The number of selected lines is determined by an external input. The active pixel region is reduced when the AE sensor is incorporated in a device having a low performance CPU, thereby reducing load on the CPU. The active pixel region is increased when the AE sensor is incorporated in a device having a high performance CPU, thereby effectively using the CPU performance to achieve higher density control.