Glass Sphere
A glass sphere is the geometrically simplest form of lens. In this photo, one can clearly see how the lens magnifies the lines in the background. The spherical aberrations toward the edges are visible, as well as another fascinating effect: the straight lines gradually become distorted into closed curves when looking toward the edges perpendicular to the lines in the background. [OPN 2023 Photo Contest Winner]
—Susanne Viezens, Max Planck Institute for the Science of Light, Erlangen, Germany