How accurate was Plato’s assertion that painters “take a mirror, and turn it round in every direction” ?

When Plato makes his assertion that painters "take a mirror, and turn it round in every direction," how much credit can we give him for his words?  On one hand, the view that artists simply hold a mirror to whatever they are trying to depict is a somewhat shallow understanding of their trade.  On the other, I think Plato is trying to convey the sense that it takes little ingenuity to replicate the physical image of, say, a person, landscape, or anything else of that matter.  It would also be helpful to consider the art in that period of time.  Abstract art is a relatively new concept, so one would think, that perhaps a good deal of art in Plato's time was in fact simple portraits of scenes that already existed in the real, physical world.  While his mirror analogy is definitely a jaded view of art, perhaps the reader can see where Plato is coming from, and interpret his message in a more charitable light.