The experiment P5.1.3.3 explores aberrations of scale. Blocking light rays in front of the lens causes a barrel-shaped distortion, i. e. a reduction in the imaging scale with increasing object size. Screening behind the lens results in cushion-type aberrations. Coma is the term for one-sided, plume-like or blob-like distortion of the image when imaged by a beam of light passing through the lens at an oblique angle.