The fly adds to the optical illusion effect of the frame; the addition of this optical illusion to works of art is believed to have begun with Christus, in the 15th century. The Trompe-l’oeil technique consists of perspective tricks, creating an optical illusion that makes two-dimensional shapes appear to have three dimensions. Other artists at the time, such as Jan van Eyck and Hans Memling, began to apply this technique in their portraits too: Portrait of Isabella of Portugal (c. 1429) and Portrait of Maria Portinari (c. 1470-72).
The presence of the fly is generally regarded as a symbol of withering or death – critics are generally divided between two different interpretations of its use; many consider the fly to have a religious symbolism, with connotations of sin, corruption, death, etc. More recently, art historians are beginning to see these images as a professional calling card; it’s believed that as the fly appears near his signature, insinuating that it could be the referent of the creator of the work. The use of the halo acts as a symbol of holiness and saints, as the figure is also a monk, showing his closer connection to God.
The light scheme used is remarkable. The monk is bathed in intense light, contrasting his figure with the space he occupies. While this hard light is typical of contemporary Jan van Eyck, Christus’ addition of a second source of opposite light behind the monk marks this portrait as distinctive. The light on the left looks like a reflection from inside the space, but it still seems to be coming from an external source, perhaps from an unnoticed window. Resulting in the light coming from inside and outside the pictorial space, and the monk becomes the connecting point of the two, allowing Christus to employ a much fuller and richer spectrum of colours and shading as if it were a single source of lighting. This complex scheme is the reason why the work looks three-dimensional and realistic.
Three quarter profile portrait, a compositional structure greatly developed in the early renaissance. To model the monk’s right shoulder more than his left, Christus drew a side of the body closer to the viewer, adding more depth to the work.
In regards to the use of colour, the use of the color red in the background is both sumptuous and disturbing which is very rare in Flemish painting. The figure is dressed in white which contrasts greatly with the warm red background.
The portrait possesses a clear physical presence thanks to the balance of composition, lighting and the meticulous and realistic rendering of details (not the smallest hair from his head or even beard is neglected). The man addresses the spectator through his intense gaze. Christus uses the light to produce a chiaroscuro effect on his face which considerably accentuates the relief effect, compared to van Eyck’s portraits. By placing a fly in the center of the false bottom edge of his canvas, he created an illusory perspective in his portrait. With this gesture, the man’s presence extends outside of the pictorial space and into the viewer’s, through the fly. Van Eyck had previously applied this trick in his Portrait of Isabella of Portugal (c. 1429), for the way she puts her hand on the false stone parapet. The false frame bears an ornamental inscription in capital letters which appears as carved in the painted frame, reading: “PETRVS XPI ME FECIT” followed in smaller print by “A 1446”. The lighting of the main text matches the one in the rest of the portrait. The date, however, probably appeared on the painting’s original frame and was added to the panel when the frame was removed.
The work was highly innovative for representing the portrayed against a detailed background, as opposed to the previous flat ones. The man is also placed in a corner of a room; thus innovating on his predecessors and even professor, Jan van Eyck. The Trompe-l’oeil technique and multiple sources of light used were groundbreaking at the time, building on van Eyck’s teachings and working on the new form of optical illusion.