4. "Medal of Alberti" by Matteo de' Pasti (Collection, Victoria and Albert Museum, London).
Thus even the simple optical vision is a phenomenon of such intricacy that it cannot be measured in all its subtle interconnections by any instrument so far invented. As a gateway to the outside world, it is one of the miraculous results of mankind's long evolutionary process. We can merely summarise its functions briefly and suggest the complex of references.
What happens when the dickeybird, or the bird of the eye, flies off? This affects not only the eyes; a person's body-soul, inspired by its goal-seeking desires and by conative will and curiosity, projects itself through the eyes towards an object. Light of a single colour is the simplest type of radiation, appearing as a single line in the spectrum. The sensation excited by monochromatic light is, therefore, the simplest type of visual sensation. But to sense even monochromatic light and recognise it involves a compulsion from within the spectator. Only through tension in the protoplasmic metabolism of the human being is it led to awareness of things in the universe outside.
Scientific observation of the human cornea lens and retina confirm the eye's similarity to a camera. But, because there is always a cameraman directing the lenses to the focus and opening the shutter, even as with any mechanical camera, the eye becomes an organic instrument or machine for perceiving things.
Until the moment of looking, there is the sensation of perception and only a little apperception, or understanding. But certain facts about the human eye complicate the pure sensation. The evidence for the existence of these facts, which are not known to common sense, comes from optical illusions. For instance, the child, in the earliest stages of its growth, sees objects upside down. The field of vision of a nine-month-old child looking into the distance is restricted. It is only through the perfecting, formative and self-regulatory processes of the body-soul that this approach is later corrected. The familiar trick often practiced by photographers who show the figure head down and legs up resembles the child's first approach. This is a common delusion. The eye slowly adjusts itself.
If you compare the iris diaphragms of the camera and of the human eye you will understand that, in both cases, when the diaphragm is contracted the image is sharpened, whereas when it is relaxed the image becomes vague. The flattening or wrong adjustment of the eye (or the camera) leaves the image blurred. The adjustment of both the human eye and the lens is carried out by the use of a sieve or screen. The use of a screen is nowadays a familiar process in printing pictures clearly, sharply and accurately. In vision, too, the image itself is broken up into dots by the rods and the cones of the retina. Each of the many cells sees one dot as big as itself. The strongest and most energetic cells receive "light" in a radiation which is reported by the eyes to the brain and other parts of the body-soul. The weak cells communicate "dark,"
If you enlarge the image of hundreds of dots, almost as in the famous neo-Impressionist painting by Georges Seurat, Port-en-Bessin, Entrance to the Harbour (Fig. 5), you can get a feeling of dissolved colour energies in a new light. The Pointillism of Seurat was based on such a formula.
5. "Port-en-Bessin, Entrance to the Harbour" (1888) by Georges Seurat. Oil on canvas, 21 5/8" x 25 5/8" (Collection, The Museum of Modern Art, New York, Lillie V. Bliss Collection).
I shall refer in detail to the findings about optical vision of Professor C. V. Raman, who has analysed the relationship to, or the impact of, our sensory impressions on the eye.1 Meanwhile, I mention here his important discovery that "light appears as a sharp type of radiation." It is appropriate, therefore, that we recognise the sensations excited by monochromatic lights of various colours as the primary or fundamental visual sensations. Likewise, when a continuous spectrum of radiation is dispersed by a prism into a band of colours, the eye can distinguish or discriminate each strip from the others in the spectrum, under the most favourable conditions of observation. And as many as 250 hues in the spectrum can be distinguished under laboratory conditions, to confirm that this also happens in the ordinary way when we look at a picture or landscape.
Walter Gropius has explained important biological facts about our ways of seeing.2 The human eye from within looks like a television camera. It transforms optical images into electrical currents through its broadcasting system; it has a supporting framework; it has photosensitive cells; it has transmitting cells; it has connecting cells; it has a nerve cable; it has a protecting base.
A more exact metaphor is the idea that "the human eye is a combination camera for day and night photography." The retinal cones are the daylight apparatus. They require much light, producing sharply defined panchromatic pictures. The rods are the twilight apparatus. They are strongly photosensitive but produce indistinct achromatic pictures.3
The discrimination of colours and of lines which takes place immediately upon the first glance is brought about by the transformer in the retina and the whole complex structure allied to perception through the evolutionary processes and the energies behind them. These energies respond to light, and, according to Albert Einstein, consist of streams of "photons."
It must be emphasised that, though the obvious analogy between the human eye and the camera eye is fairly accurate in relation to the first impact of a work of art on the retina, the experience of seeing involves much more than this initial impact. The vasanas (energies or vitalities) of the body-soul urge us to active collaboration. The urge behind seeing a painting or sculpture has subjective associations of all kinds. These may in rare cases be refined, and we may set a subjective-objective condition for seeing, but, beyond this, there is achieved an undefined union, catharsis or release.
Consequently, as soon as the dickeybird flies off towards the "photon" energies of a picture, with its own impetuous vitalities, it transforms the report immediately, with some additions or subtractions, and relates it to the centres of apperception. The energies of the body-soul, behind the television-like apparatus inside the retina, take over. And discrimination between the various parts of the image, which began immediately when the energies of the picture hit the retina, now begins to be heightened. The image is thus already being seen into. It is now allied with the surviving primitive anthropoid brain in us all, the thalamus, situated underneath the cerebral cortex. The image now travels towards the cerebral cortex. Recharged by memory, it goes towards the lumbar ganglion and the complex of nerves, tendons, muscles and subconscious underlayers. Thus it spreads its subtle rhythmic and other messages down below the far-flung universe of the unknown life of man, within the five-or six-foot structure that has evolved into the miracle called the human being. In so far as the eye selects the visual features, according to the choice compelled from within by the sensibility of the person looking, as well as by his potentialities for intense feeling and thinking, the eye becomes the seeing window of the body-soul, which is replete with all the biological and racial experiences that have gone into the making of the metabolism.
As the onlooker contemplates a painting, his nervous organism, in a flash of lightning, registers many sensations, even in the first one or two seconds. Beyond the dickeybird, the other birds of his inner faculties carry messages from one to the other, so that, ultimately, he has an aesthetic experience.
The available evidence about the responses of animals, birds and insects shows that, in some respects, they are more sensitive than human beings. For instance, birds have vision that is about one hundred times more acute than ours, and they can also sense magnetic fields. With their compound eyes, bees can detect the direction of the sun's rays and thus buzz about by "celestial navigation"; bats can hear supersonic sounds; and snakes are sensitive to the slightest temperature changes.4 Man, however, is superior in so far as he has evolved
