Vignette 4: Realistic Painting as Illusion
Aristotle distinguished between essence and accidents. For example, if you come to my office and I ask you to take a chair, you will have no problem doing so even though you may have never seen that particular chair before in your life. How then do you know it's a chair? Apparently a chair has an essence, "chair-ness" if you will, that allows you to recognize it and keeps you from sitting on the coffee table. But when one paints as a realist, one must not paint "chair-ness." A stick figure of a chair will capture "chair-ness" but it won't be the particular chair. The essence of a chair is an abstraction, and if you enjoy abstract painting, you may paint it in a variety of ways. But a realistic painting of a chair (or anything else) must be particular. It must include the accidental (non-essential) features: shadow, color, perspective; these are accidental properties. Ultimately, every realistic painting is a two-dimensional illusion of a three-dimensional object. Sometimes the illusions are so convincing they baffle, but they are illusions nonetheless. We must learn to paint a convincing illusion. It must be an illusion, because the real world is three-dimensional and the canvas is two-dimensional.
Experience in the world and the visual apparatus conspire to color our perceptions. When painting realistic scenes, art teachers often exhort their students to "Paint what you see." This is a call to paint the accidents rather essence or abstraction. For example, a yellow banana under a dim light may reflect exactly the same hue as a green banana under a bright light, and whatever hue, value, and chroma that is, we must do our best to construct an illusion of it using paper, pencil, and paint. In the meantime, your visual apparatus and your mind are working in tandem in the opposite direction to uncover essence. I'll show you. Consider the following figure.
Figure 1. Constancy of Color.
The left panel of Figure 1 shows a colored checkerboard. The middle panel is the same checkerboard under a blue filter. Yet, somehow, we can still perceive the yellow squares even though the blue filter has clearly changed their hues compared to the leftmost panel. On the rightmost panel is the same checkerboard, this time under a yellow filter. Even though the yellow filter has modified the hues, we are still able to perceive the blue squares underneath the filter.
Now for the shocker. The circled squares under the blue and yellow filters have identical hue, value, and chroma. No, you say. The yellow squares under the blue filter are clearly yellower than the blue squares under the yellow filter. No, they are not. Hmm. Well surely the value of the two squares is different, the blue under the yellow being darker than the yellow under the blue. Wrong again. Your perceptual apparatus is accommodating the various filters to estimate the yellowness or blueness of the underlying color. However, if I show the squares in isolation (Figure 2, below), you will see that the hues are identical. How could it be any other way? Can blue under yellow really be different than the same yellow under the same blue? No, and it isn't.
Figure 2. Colors Revealed.
I know. You still don't believe me. So, make a couple of small holes in a piece of paper and place one hole over a "yellow" square in the middle panel of Figure 1 and another hole over a "blue" square in the right panel being careful to not let any of the surrounding context show. You will see that the squares are identically gray. (Blue and yellow pigments do NOT make gray. However, a blue filter over yellow pigment, or vice versa does result in gray. For details, see the Chapter 1. Perception of Color and Color Models.
What is happening? In the middle panel of Figure 1, your perceptive apparatus is adjusting the hue perception to subtract out the blue from the gray allowing you to perceive the yellow "underneath." Similarly in the right panel of Figure 1, your perceptive apparatus subtracts the yellow filter from gray to allow you to perceive the "underlying" blue. The stimulus is ambiguous. It could be gray. It could be yellow under blue. It could be blue under yellow. So your God-designed visual apparatus looks to the context to interpret the ambiguity. However, if you want to paint the above figures correctly, you will mix the same gray for the blue-filtered yellow squares as you do for the yellow-filtered blue squares. And when you do, the squares will look as if they are yellow under the blue filter and blue under the yellow filter even though they have identical hue, chroma, and value. Realistic painting is an illusion of reality. It is flat but it looks three dimensional. It is uniformly lit, but appears to have light and shadow.
Shadow
The perceptual apparatus is also designed to maintain hue, value, and chroma constant even as the lighting varies. If you know that a bell pepper doesn't really change color from shadow to sunlight and you paint your perception, you will paint both conditions with the same paint and you will be WRONG, because the paint must have lower value and different hue to give the illusion of shadow. And it IS an illusion. There is no shadow on the painting; you must simulate it.
Shadow and Depth
How do you know that a surface is rounded or curved in real life? A rounded surface will have a lighter value in the direction of the light source that graduates to darker value at its edges. If you want to see a curved shape in real life, you put it in the light and everything takes care of itself. If you want to create the illusion of a curved surface in a painting, you need to graduate the pigment from light to dark or things will look flat and unrealistic. A painting is of course flat, and flatness is unrealistic. But the artist has to create the illusion of reality.
Transparent and Reflective Media
How does one paint a transparent container? One looks with care at where light is reflected. One looks at the distortions the glass makes and accurately draws them. One notes that the transmitted hues of the background have lower chroma behind the glass to create the illusion of transmissive loss of light through the glass. (If the background hues are identical behind and around the glass, then the glass isn't transparent, it's invisible! If you omit the background "behind" the glass to leave white paper, your glass is not transparent, it's opaque white.) Even subtle differences are noticed immediately by the eye, which has been trained by experience to recognize them.
