A method includes obtaining a plurality of object images taken by an image pickup device while moving a focal position within a predetermined range, the image pickup device being capable of taking images at arbitrary focal positions within the predetermined range; calculating a first in-focus position within the predetermined range based on pieces of contrast information on a manually-taken object image group, the manually-taken object image group including the plurality of object images taken while manually moving the focal position within the predetermined range; and calculating a second in-focus position within the search range based on pieces of contrast information on an automatically-taken object image group including the plurality of object images taken while automatically moving the focal position within a search range, the search range being determined with reference to the calculated first in-focus position.