Image processing apparatus, control method thereof, and storage medium

An image processing apparatus comprises a motion vector detection unit, a generation unit for generating information regarding the motion vector as metadata, a recording unit for recording each frame image in association with the metadata; and a control unit for causing the motion vector detection unit to perform motion vector detection by using an image signal on which reduction processing or thinning processing was performed, and causing the motion vector detection unit to determine an image area based on the metadata and to perform motion vector detection by using an image signal on which reduction processing or thinning processing was not performed or on which reduction processing was performed using a smaller reduction ratio than that used during the image capturing operation or thinning processing was performed using a smaller thinning ratio than that used during the image capturing operation.