Contrary to popular belief, and the mystique cultivated by some artists, painters don't generally paint without some sort of reference available.
Whether it's a photograph of the subject, sketches they've created for the painting, or some other form of visual reference they can look at as they paint, there are very few artists who work without reference.
Iconic painter Norman Rockwell was no stranger to using reference photos in the creation of his works, and even though most of his paintings look like a spontaneous moment captured in time they were often based on carefully staged photographs.
Here's one of his famous paintings- The Tattoo Artist:
And here's the reference photo he used for the sailor getting tattoed, a profile shot of Rockwell's neighbor Clarence Decker, who managed to have an even dopier expression on his face in the photo than he does in the painting!
See more reference photos Rockwell used to create his iconic paintings over at Beautiful/Decay