try following texts from art historian Ernst H. Gombrich: - Art and illusion : a study in the pictorial representation, Pantheon books New York, NY, copyrighted 1960 - The image and the eye : further studies in the psychology of pictorial representation, Phaidon Oxford, 1982 they're not too difficult to read. sincerely Meret Ernst ---- To signoff SCREEN-L, e-mail [log in to unmask] and put SIGNOFF SCREEN-L in the message. Problems? Contact [log in to unmask]