A portrait can be ruined by an eyelid being a millimetre out of whack. With ellipses (the intersection of a plane by a cone – i.e. the shape of a round thing viewed from the side), it is also a matter of millimetres. I suspect most painters’ studios have a graveyard of failed canvasses in the corner where the dreaded ellipse has gone wrong … along with an eyelid or two.
I decided to tempt fate by painting a disposable coffee cup that combined an ellipse with a turned up spout. What a nightmare. Never again.