1. A photometric device, comprising: an imaging unit that captures an image formed by an optical system, with a marker capable of switching between display and non-display disposed in a light path of the optical system; and a correction unit that, based upon a difference between a first image captured by the imaging unit in a state where the marker is displayed and a second image captured by the imaging unit in a state where the marker is not displayed, performs a correction of a third image that is different from the first image and the second image.