Ellipse Perspective: Coin, Can, Glass

From Draw Like da Vinci, p. 48: Disc perspective – exercise round the oval. A disc retains its circular shape only when viewed face on. It becomes oval (an ellipse) when viewed obliquely, because its surface is foreshortened. You see a full circle when you spy a coin on the pavement directly between your feet or when you look directly above at a ceiling light or face a fan. The more oblique the viewing angle, the less surface you see. When viewed side-on at eye level the surface disappears altogether, leaving only the edge of the disc in view. Notice that, below eye level, the base of the can (and glass) has a wider ellipse than its top. Conversely, above eye level, the top is rounder than the base.