A signal processing unit subjects to signal processing first image signals, obtained as the output from a three-sensor-system sensor unit which uses CMOS sensors or the like, thereby obtaining high-image-quality second image signals. The three sensors are positioned at placement positions which are suitable for signal processing at the signal processing unit. The suitable placement positions have been obtained by learning performed beforehand. In one arrangement, the signal processing unit evaluates the second image signals, and controls the placement positions of the three sensors according to the evaluation results. In another arrangement, the first signals are evaluated in a predetermined region, and the capabilities of the sensors at the predetermined region are changed according to the evaluation results. In another arrangement, the sensor unit is controlled according to the level distribution of the first image signals. The present invention can be applied to still or video digital cameras.