An image apparatus includes a screen, a detecting unit, a determining unit, an acquiring unit and a control unit. The screen is configured to display an image formed by an optical system and at least one detection position superimposed onto the image. The detecting unit is configured to detect information regarding focus of the optical system at the detection position. The determining unit is connected to the detecting unit and configured to determine whether the information regarding the focus is within a predetermined range. The acquiring unit is connected to the determining unit and configured to acquire first image information at the detection position when the determining unit determines that the information regarding the focus is within the predetermined range. The control unit is connected to the acquiring unit and configured to evaluate arbitrary second image information in the screen using the first image information.