An image pickup apparatus is provided with a number-of-pixels reducing circuit arranged to form a reduced image by reducing to a predetermined number the effective pixels among all pixels owned by an image sensor in such a manner that the method for reducing the effective pixels changes when the image pickup mode of the apparatus is set to a first mode (a small-image-plane image pickup mode). The number of effective pixels is reduced in a manner apposite to the situation in which an image is picked up. Exposure control is performed appositely to the reduction of effective pixels, so that depiction can be effectively made by taking advantage of the effect of depth of field, etc., according to the situation.