Go to a museum - any art museum. Look at the Old Master Portraits.
You won't see any great big toothy grins. Notice that every single one of them painted their subjects with closed-mouth smiles.
Mug Shot of Tom Delay, House of Representatives Majority Leader (2003 - 2005), Republican, Texas.
Evidently Tom got all spiffed up for his arrest photo. Although it was obviously the best photo in the stack, it would still make a really crummy painted portrait. And not just because it is an unimaginative Mug Shot - it sports a big toothy grin.
And big toothy grins are a big "no-no in" portrait painting.
Don't paint anybody with an open mouth!
Karin Wells (and you can quote me)
The eyes are "the mirror of the soul" - the Old Masters knew this and in their paintings, they wanted the eyes to show as much as possible and often allowed the sitter's eyes to engage the viewer.
When someone gives you a big toothy smile - the eyes narrow into slits. When the mouth is closed and smiling, the eyes will be open much wider.
Let me prove this to you:
Stand in front of a mirror. Give yourself a great big grin and then freeze that grin. Notice that your eyes have become narrow slits.
Then, still freezing that toothsome grin, open your eyes as wide as possible.
Scary face, eh?
Note: As soon as I can convince someone to agree to pose for me doing this, I'll post a picture here to illustrate. In the meantime, I paraphrase and repeat myself:
Don't ever paint anyone with a big toothy grin!
Karin Wells (and you can quote me again)
It is especially difficult to do a photo shoot of a child because so many of them tend to grin when they see a camera pointed at them.
I often "pretend to shoot" until the child is bored enough to interact with me, forgets the camera and stops "mugging."