1. An image processing method comprising: sensing an object without performing light projection with a light projection unit and acquiring a first image expressed with a plurality of colors; sensing the object while performing light projection with the light projection unit and acquiring a second image expressed with a plurality of colors; extracting pixels at which chromatic differences of the respective colors between the first image and the second image fall within a predetermined range; calculating a sum pixel value of the extracted pixels for each of the plurality of colors; and calculating, for each of the plurality of colors, a correction value for a color balance processing of a still image based on a ratio of the sum pixel value of each of the plurality of colors of the extracted pixels to a value obtained by averaging total value of the sum pixel values of all of the plurality of colors of the extracted pixels by the number of the plurality of colors.