1. A method comprising: calculating image capture parameters of an image capture device for an ocular area of a subject, the image capture parameters used for enhancing a corneal glint; capturing at least three different test images of the ocular area, each of the different test images recorded at a different measurement position relative to the ocular area, the different measurement positions achieved by adjusting a focal length of the image capture device; calculating a defocus measurement for each of the at least three different test images at the different measurement positions using the corneal glint; determining an estimated focal point of the ocular area using the at least three different defocus measurements; and capturing an image of an iris of the subject at the estimated focal point, the image used for biometric identification.