If you want a portrait likeness, don’t paint exactly what you see.
John Singer Sargent certainly didn’t copy appearances, as this photo/painting comparison attests. He exaggerated the character of his subject, Coventry Patmore. Sargent made the neck longer, the hair fuller, the face bonier, and the mustache more “twirly.”
To be clear, the painting was done from life, not from the photo, but both date from the mid 1890s.
Patmore was so impressed with Sargent’s interpretation of him that he wrote: “He seems to me to be the greatest, not only of living English portrait painters, but of all English portrait painters; and to be thus invited to sit to him for my picture is among the most signal honours I have ever received.”
From the book John Singer Sargent by Richard Ormond, 1970, figure 21 and 22. Thanks, Barry!
ADDENDUM: Don't miss the fascinating string of comments on the subject of sight-size practice.