Abstract: The outputs of N kinds of spectral response characteristics from an image sensor are passed through low-pass filters to obtain N kinds of outputs from the 1st through Nth, and the output signal of a pixel of interest having the Kth (1.ltoreq.K.ltoreq.N) spectral response characteristic is multiplied by the ratio of the low-pass filter output of the image sensor output at the coordinates of the pixel of interest to the Kth low-pass filter output at the coordinates of the pixel of interest, thereby the luminance signal with alleviated attenuation of the harmonics components is obtained.