The influence of oriental culture, which came by way of Constantinople and through trade in luxuries with the East, was especially strong in medieval Venice. It is evident here in the almost barbaric display of gold and brightly colored stones of which this mosaic is constructed. The fantastic jewelled sprays of flowers are especially lavish in their brilliance. They sparkle in pure contrasting colors with no attempt at shading.
The ancient Roman style of deep, solid, naturalistic painting has been abandoned. Instead, we have a picture almost entirely in one plane, with more distant figures placed above the nearer ones, as in Persian miniatures. This destroys realism, especially in the huddled group of sleeping men, where spatial intervals are ignored. Shadows, too, instead of being placed and graduated naturally, are made into dark heavy strips that outline stiff drapery folds and crevices in the rocks. There is some individuality in the sleeping faces, but much less than in Renaissance painting, and the face of Jesus is conventionally impersonal. Postures, too, are cramped and immobile.
All these qualities, which are faults according to Renaissance standards, have a different value as contributing to the kind of decorative effect sought by Byzantine artists. The heavy, narrow shadow-streaks produce a flow of wavy, jerky lines that stream briskly up and down. Since the distant figures, like those of the kneeling Jesus, are as large and distinct as the nearer ones, the upper part of the design is not vague and dull, but a clear, emphatic part of the two-dimensional pattern. There is no attempt to dissolve the wall, and give the illusion that it opens out into space. A wall is expected to be a wall; it should appear as well as be solid everywhere; and that means decorating it with a fairly uniform flatness, throughout.
The three figures of Jesus are arranged as the corners of an inverted triangle, while the rocky peaks point upward. The plants, the garment-folds and crevices are full of smaller angles in all directions. Thus the whole composition is knit together in a zig-zag, vibrating rhythm.
This picture is but a section in a connected series along the wall, and the eye is led from one part to another (here from right to left) through successive episodes of the story, encountering the figure of Jesus in different situations. This way of looking at the parts of a picture in a definite temporal order (somewhat as we look at a moving picture) is common in medieval and early Renaissance art in Europe, and also in the landscape scrolls of China. An interesting element in art was lost when the strict realism of the later Renaissance insisted that a picture contain only what could be seen all at once, from a single point of view.
Throughout the Basilica there are many other excellent mosaics of the Byzantine period: for example, Building the Tower of Babel in the atrium (notice the variety of angular movements) ; and Events in the Life of John the Baptist in the baptistery (a fine decorative arrangement of gorgeous costumes, against a background of architectural elements, much distorted in size and perspective to bring them into the pattern).
Other mosaics (upstairs and on the outside) are much later, and are made in imitation of Renaissance painting, with attempts at natural flesh tints, light and shade, gesture and deep space. These attempts are unsuccessful by comparison with good painting, mosaic being too inflexible a medium to secure them easily. At the same time, they lose the decorative appeal of bright, flat, non-realistic color-design, to which mosaic is especially suited. Thus the mosaics of the Middle Ages, like their tapestry and stained glass, are on the whole superior to those of later centuries, because of their greater harmony between form and medium.