image fig1 shows a weighting and integrating circuit 130 in the auto focusing circuit 100 the image signals e g represented by arrow 109 derived from predetermined pixels on imaging device are input into the pre gamma correction circuit 110 the pre gamma correction on the image signals 109 the pre gamma correction is based on the s shaped function 310 the pre gamma correction circuit 110 multiplies the input signals by the slope of the pre gamma function 310 in the appropriate luminosity range the pre gamma corrected image signals e g represented by arrow 134 are fed to the spatial filtering circuit 120 which emphasizes the edge components of the image using a filter such as those shown in fig1 12 and 13 the filtered image signals are input into the weighting and integrating circuit 130 which averages the filtered image signals to generate an average weighted signal the weighted and integrated image signals are fed to the cpu 140 the cpu 140 receives the weighted and integrated image signals also referred to as the auto focusing signal and produces the driving signal to drive the focus motor 150 based on the received signal the focus motor 150 moves the.