A method for testing defocus of a camera includes providing a vehicular camera and providing a defocus tester that includes a first target disposed behind an optic and a second target that is not disposed behind the optic. The first target has a simulated image distance relative to the vehicular camera that is different than an actual image distance. The method includes positioning the defocus tester relative to the vehicular camera such that the vehicular camera views the defocus tester and images (i) light that has reflected off the first target and passed through the optic and (ii) light that has reflected off the second target and not passed through the optic. The method includes capturing image data with the vehicular camera that is representative of the first target and the second target and estimating a defocus of the vehicular camera responsive to processing the image data.