Realism is a kind of naturalism that even if the subject is imagined it still has a surface naturalism. With Idealism things are not real but are ideal, or made how they should be. Realism and abstraction are what makes up two opposite approaches of representation. A photograph is seen as kind of unoriginal and you see all of lifes imperfections.
Painting can let the artist concentrate on a certain subject without interferance of other objects.
It's easier or I should say a no brainer to take a photo, but to paint a picture takes alot more talent. In Thomas LeClears painting Interior with Portraits it can be seen that he is making a statement about photography. The book suggests that by not showing the photographers head the painting might suggest that it doesn't take much though to take a picture. Classical art comes from the Greek and Romans. It mainly is related to idealism.