A quick sketch of David at the Accademia, Florence Friday before last. David's well lit, but he could do without the directed light they've aimed into his eyes. Michelangelo carved David's deep-set eyes so that the upper part of the irises would be cast in shadow. Directing a light into the eyes counters that effect and gives David a dazzled look. Other than this issue, his lighting is perfect.
Many remark on David's large hands. The enlargement of the hands relative to other body parts dramatizes David's ability to defeat Goliath -- which he achieved, according to myth, with only a sling-shot. His hands are therefore very important and the emphasis of their size is consistent with an artist's goal to dramatize their strength and to direct our attention to them. I've noticed that photographs tend to capture the emphatic proportions in a way that makes them appear overdone. Michelangelo would not have known how his work would look in a photographic image. Seeing David at the Accademia, I personally don't find the emphasis of the hands to be overdone.
A reason for why Michelangelo can stylize the figure in that way is because of how we perceive a colossal scale figure. When we look at a colossus -- in reality, not via a photograph -- we look at one part of the figure and then another, and we continually "rove" our eyes across the figure, bringing together what we perceive. We don't "see" the figure the way a camera does -- in one glance that captures all parts at once.
A related issue is addressed by David's large head -- large relative to the rest of his figure. David was originally intended to be mounted up high which would have greatly foreshortened the figure for the viewer on the ground. Even while he is on the base on which he is set currently, David's head is foreshortened, and its size "looks right" when viewed from the floor of the Accademia. Seeing David in photographs is no substitute for seeing him "in the marble" at the Accademia.
Modern interest in David's body proportions can distract viewers from what is most important about David, which is that he is a rare colossus that successfully embodies a vision of human grandeur.