This is more of an artist thing, but... I can either draw the FL from my novel "Damsel in the Red Dress" really well, or I can draw her looking consistently like herself. It appears there is rarely an in-between. If the picture looks super crisp, I'll come back later to realize something about her eyes or face shape no longer makes her look quite like she's supposed to.
And I just can't draw Essence (FL from "A Dozen Morning Glories") consistently at all. Period. A dozen different kinds of pretty, but they all look like different people