““Let me tell you what I do when I am painting. First of all, on the surface on which I am going to paint, I draw a rectangle of whatever size I want, which I regard as an open window through which the subject to be painted is seen; and I decide how large I wish the human figures in the painting to be. I divide the height of this man into three parts, which will be proportional to the measure commonly called a braccia; for, as may be seen from the relationship of his limbs, three braccia is just about the average height of a man’s body. With this measure I divide the bottom line of my rectangle into as many parts as it will hold; and this bottom line of the rectangle is for me proportional to the next transverse equidistant quantity seen on the pavement. Then I establish a point in the rectangle wherever I wish; and as it occupies the place where the centric ray strikes, I shall call this the centric point. The suitable position of this centric point is no higher from the baseline than the height of the man to be represented in the painting, for in this way both the viewers and the objects in the painting will seem to be on the same plane.” Leon Battista Alberti

In this paragraph, Alberti outlines a formula for perspectival painting that entails (1) a rectangular frame, (2) the window as a metaphor for the frame of the painting, (3) the “subject” that is seen through this frame, (4) the human figure as a standard of measure and as determinant of the “centric point,” and (5) the immobility of the viewer. 

Alberti’s text serves as my starting point because of his striking use of the architectural figure of the window. Alberti’s Renaissance metaphor of the window has haunted centuries of subsequent thinking about the humanist subject of perspective, and has remained a defining concept for theories of painting, architecture, and moving-image media.”