Here's the thing nobody warns you about: if you learn the average grid and then make every face obey it perfectly, all your portraits come out looking like the same polite stranger — a generic mask, technically correct and recognisably no one. The average is where you start, not where you finish.
The Trap: Forcing Every Face onto the Textbook Average
Real heads break the averages constantly, and a real likeness is nothing but a careful record of exactly how a particular head breaks them. Capturing each person's deviations from the average is what makes a drawing look like them rather than a generic face. Force a real person back onto the textbook proportions and you rub out the very thing that made them recognisable.
Where Real Faces Wander Off
Think about someone you know well. Maybe their eyes are set a touch wider apart than one eye-width — that's the look. Maybe they've a longer chin, so the bottom third runs deep. Maybe a high, open forehead that pushes the hairline up and stretches the top third. None of these are mistakes; each one is a fingerprint. Drag a single slider in the toy and you'll feel it: nudge the eyes wider and a stranger appears; lengthen the chin and it's a different stranger again. You're not breaking the rule, you're measuring the deviation — and the deviations are the person.
The Quiet Skill: Read the Gap, Don't Ignore It
This is why portrait artists spend so long looking before they commit a line. They're not re-checking the average — they know it cold. They're hunting for the differences: where does this nose-to-chin third run shorter than the books say, where do the eyes sit a hair higher? The grid from rung two is the ruler you hold the real face against. The drawing happens in the gap between the two.