1. An image processing apparatus comprising: an acquisition unit configured to capture image data including effective area data read out from pixel output elements within a preset range of an image pickup device and ineffective area data read out from pixel output elements outside the preset range of the image pickup device, for correction of a value of a pixel of the effective area data wherein the image pickup device includes a defective pixel output element; a signal generation unit configured to superimpose a first signal indicative of a position of the defective pixel output element of the image pickup device and a second signal indicative of a position of each of the pixels outside the preset range of the image pickup device, to thereby generate a defective pixel determination signal indicative of a position of a determined-as-defective pixel; and a correction unit configured to be operable when a target pixel in the image data is determined as the determined-as-defective pixel based on the defective pixel determination signal, to correct a value of the target pixel in the image data, using values of the image data associated with ones of pixels positioned around the target pixel, the ones being each not determined based on the defective pixel determination signal as the determined-as-defective pixel.