Dear All,
For getting a likeness, there is probably nothing like real life and reference photos and improving on what we see. At least for most of us.
However, the Mexican artist, Gregorio, painted my grandparents from life and he painted them from memory and both looked exactly like them so I know that the feat can be done successfully. (He painted a lot of stamps for the Mexican government back in the 70's. Mostly airplane stamps. He was an illustrator also for a Mexican book about the Indian history of Mexico).
Would we want a genuine J. S. Sargent portrait that he painted strictly from memory or imagination? Would it be equal to some of his other great paintings? Surely no one would value it less because he painted it from memory or his imagination. His genius would transcend the process, wouldn't it?
I think Mike had a good point. Quote: If someone can produce great portraits from photographs, from life or from memory, that's fine, but they have to be great first, without the knowledge of process.
I think you are right Michael, the ship changed course somewhere along the line.

But it surely is interesting to see all the different insights. Very delightful.