When I was drawing those Preston Blair head shapes, I was wondering what makes a shape like that tick, how can you best see an ellipse, egg shape and pear shape through the artist’s eye?
Well, an ellipse is straight forward. That is an elongated circle.
An egg shape is based on an elongated circle, but it is elongated more on one side than the other. Furthermore, the more elongated side is thinner and the less elongated is fatter than a comparable ellipse.
A pear shape is like an egg shape, but with a pinch in the more elongated side of the shape. This pinch makes the already thinner side even thinner, and the fatter side gets even fatter.
So an egg shape is just a special case of a pear shape, while an ellipse is a special case of an egg shape, and a circle a special case of an ellipse. Of course, by logic, a circle is also a special case of a pear shape.
That is all.