1. A camera apparatus comprising: pixel information forming means for forming pixel information constituting a display screen based on pickup output signal obtained through a lens block; reference measurement frame setting means for setting a reference measurement frame with a predetermined size on a predetermined position on said display screen; detection measurement frame setting means for setting a detection measurement frame with a predetermined size on said display screen; standard frequency characteristic data forming means for forming standard frequency characteristic data for a brightness level and/or hue angle based on brightness and/or hue information on an image in said reference measurement frame; detection frequency characteristic data forming means for forming detection frequency characteristic data for a brightness level and/or hue angle based on brightness and/or hue information on an image in said detection measurement frame; similarity calculating means for calculating the similarity of said standard frequency characteristic data and/or said detection frequency characteristic data by several methods; effective similarity calculation method selection means for selecting the most effective similarity data on the screen among a plurality of similarities obtained from said similarity calculation; detection measurement frame determination means for determining said detection measurement frame with a higher similarity by using the similarity calculation method selected by said effective similarity calculation method selection means; and pixel information modification control means for controlling said pixel information forming means so as to match the position of said pixel information on the determined detection measurement frame with the position of said reference measurement frame.