This chapter is about Alberti’s frame and concept about perspective view and a window as a frame. She explain the elements such as the frame, point of view, the subject to be painted, and the viewer.
Alberti regards the picture as an "open window". He demonstrates his attraction to the illustrative powers of metaphor to enrich his abstract reduction of the phenomenal world of vision to the mathematics of point, line, and surface.
Alberti also supplies us with a Renaissance root for the concept of a windowed "elsewhere", not a realism of subject matter but a separate spatial and temporal view. The spectator's experience of "gazing" through the window had its own spatial effect - and yet this new perspectival realism of representational space did not imply realism of subject matter, nor, as we will see in a moment, did it imply a temporal realism.