Aberrations. We have often approximated sin?= ?Deviations from our formulas due to this approximation and others we have made are called aberrationsSeveral kinds of aberrations are observed. Aberrations. Spherical aberration and circle of least confusion. Aberrations. Off-axis objects don\'t focus properlyImage of a point is not exactly a circleFocal plane is not flat OK in eyes since retina is curved and most vision is at fovea but bad for camerasCorrect with multiple lenses.