The Trompe l'Oeil ("trick of the eye") golden glow surrounding Joseph and the Madonna and Child is shaped like a gothic stained glass window-within-a-window. Yellow rays form the border, shaped like the actual gothic windows in the cathedral. The red circle behind Joseph's halo is constructed like a roundel of stained glass. Even the lower part of Joseph's mauve robe, and the protective green curtain, are rendered less as drapery than as stained glass.
In contrast to the Trompe l'Oeil elements, the figures are all naturalistic, particularly the new mother.