1. A method of detecting a compositional change in an image, comprising: obtaining an electrical signal corresponding to an illuminance of the image formed by a focusing lens using a photoelectric detector; dividing the image into a plurality of subdivision areas; calculating, for each of the subdivision areas, a focus evaluation value representative of an amount of high frequency component contained in the electrical signal and a brightness value representative of a brightness of the image; storing as reference values a focus evaluation value and a brightness value of the image in focus; sorting the subdivision areas according to an object distance classification; weighting with different weights the subdivision areas in classes of the object distance classification based on a main subdivision area to which a main object belongs; comparing the focus evaluation and brightness values after a focus with the reference values so as to calculate variation in the focus evaluation and brightness values; and detecting compositional changes based on the weights as well as the variation in the focus evaluation and brightness values.