Stereopsis and Depth

This week, the readings have had a huge impact on the way I look at the world. Sacks points out that "the subjective quality, the quale, of stereopsis is unique and no less remarkable than that of color". Like color, stereopsis is an aspect of vision that I had never taken the time to consciously notice. Reading Sacks' article on Mr. I earlier in the semester caused me to really consider the presence of color in my actual field of vision, in terms of its practical importance. Previously, I had only really paid attention to the importance of the symbolism we attribute to color, especially in an artistic expression. While I felt intrigued by this new perspective on color, it can't compare to what I felt upon reading Sacks' article about stereopsis. Sue's letters to Sacks were extremely evocative for me, and it probably took me at least half an hour longer to read the article than it should have, as I was constantly looking away from the page, covering an eye, and trying to view my surroundings as someone with monocular vision might. I have a very hard time picturing the 2D world that monocular vision presents, I think because stereopsis is just so inherent in my own vision. Just as Sue couldn't imagine stereoscopic vision (or that it would improve her perception of the world), I cannot imagine viewing the world without it. I was especially intrigued by Sue's diary excerpts: "When I was eating lunch, I looked down at my fork over the bowl of rice and the fork was poised in the air in front of the bowl. There was space between the fork and the bowl. I had never seen that before. . . . I kept looking at a grape poised at the edge of my fork. I could see it in depth." Not once have I ever thought of things as 'in depth'- but now it's all I look for. Even now, as I write this, I am suddenly kind of shocked by the way my computer sits in space, between myself and the wall in front of me. I'd never consciously noticed this kind of placement. I can't imagine the shock Sue must have had the first time she saw things as 'popping out' toward her. It must have been like an unexpected Magic Eye picture.

All of this thinking about depth is making me curious as to how artists play with our depth perception. Last week we read a lot about how artists were able to employ various techniques, like shape from shading, in order to create the sense of depth upon two dimensional canvases. These works were concerned mainly with depicting an accurate portrayal of a scene. But I wonder about the effect of an artwork that intentionally tries to play with our perception of depth; how this can be achieved. We've mentioned View-Masters and Magic Eye pictures, which both take advantage of the eyes' positions in relation to each other. These seem somehow more sensational or novelty-like than artistic. However, there are some stunning modern works that I can think of that take advantage of our depth perception to artfully manipulate our experience of the work.

The piece that I kept thinking of during our class discussion last week, and while I was reading for this week, was a sculpture by Anish Kapoor called The Healing of St. Thomas. Here is a picture:

As Chris Bergeron wrote in 2008, "Instead of carving marble or forging bronze, Anish Kapoor sculpts with materials that can't be held like mirrored reflections, the laws of optics and space around your body." Kapoor's work is extremely evocative, as he is able to really change the way you experience what you see. For some reason, The Healing of St. Thomas seems to me to be especially relevant to our discussion about depth. I saw the work in 2004; I entered the room from the left side of the wall, so that I was walking parallel to the wall. At first I couldn't even see that there was an artwork on the wall; then, as I approached the centre of the room, I saw what appeared to be a dash of red paint across the surface of the while wall. As you can see from the picture, neither the white of the wall nor the red color of the paint really show any shadow; they seem to really absorb light. The paint actually covers the internal surface of a kind of inverted wedge carved into the wall. I think that what is so striking about this piece, to me, is the fact that its depth only makes itself known once the observer has spent time and effort viewing the piece from multiple perspectives. Also, once you realize what you are really looking at, suddenly the emotion of the piece is revealed. What appears to be an innocuous splash of red paint is actually an extremely evocative wound, reminiscent especially of the wound in Christ's side on the cross. Homi K. Bhabha wrote a very powerful essay on this piece, in which he illuminates the importance of viewing the work from multiple view points, and I'd like to quote some of it here:

The wound gathers like a gaping aura, drawing us to it – disciple, artist, writer, viewer – to witness the making of a miraculous rebirth, the Resurrection, through the repetition of a shape, the void, each time for a different purpose.[...] You lead me to the precise position and location of the wound.Just this red slash, and nothing else, and yet, somehow, the space around it comes alive, making an expanded emptiness, beyond the supporting wall, to bear the wound…, I observe.

Kapoor plays with our pre-supposed visual norms a lot, and I really reccommend taking a look at his website (www.anishkapoor.com), where there are photographs of a lot of his work. Obviously, the full effect of their shape and color can't really be conveyed through the flatness of photography (just as the complexity of depth in the world cannot be conveyed fully through flat images), but you can get the idea.

Kapoor's work doesn't necessarily capitalize on stereopsis, but it does play tricks tha cause our brains to confuse three dimensional objects or shapes for flat surfaces, and I think the implications of this are really fascinating. I especially like the fact that to fully understand the true shapes employed in his sculpture, one must view the work from multiple angles, and one must spend time integrating the possible meanings of the piece into ones literal physical interpretation of the piece. Because we get the scriptural reference inherent in The Healing of St. Thomas, we are able to perceive it as a wound in the otherwise blemish-free wall, and not as simply a painted concavity. I can't think of any other work I've seen that does this; does anyone know of another artist whose work has this effect?

The Law of Simplicity

In his chapter on Growth, Arnheim introduces the Law of Differentiation, which helps me understand why I have not hitherto managed to post any image examples on this blog. Ah-ha. I am at this point not quite capable of being moved by visual phenomena, not without rigorous analysis and aid of other intelligent brains. Nor am I much lettered in art history. Well what's the solution? Is the solution for me to go to a museum and look at works of great genius? As Arhneim states in his introduction "mere introduction to masterworks will not suffice." No, essentially, I am at the level of the primitive, in which forms are highly undifferentiated, and representation is manufactured with the crudest possible schemata. I will have to start at the bottom, and work my way up from the bottom.

What's marvelous is that the chapter on Growth (which I know was not the reading for this week) equates the developments of art history with the development of our visual capacities from birth, so that both paths parallel each other. And meaning that those of us in our maturity who wish to perhaps start from scratch need do no more turn to the history of art, and begin at the beginning.

Arnheim makes it possible to view artistic creation as a narrative. In other word, we can pose a problem or question such as "how is the artist going to represent such and such a phenomena on a two dimensional canvas using colored paints?" and then follow the protagonist (the painter) or the collective protagonist (painters and artists throughout history) as they find ever more complex and effective solutions to the problem. Obstacles present themselves (the introduction of central perspective makes it more difficult to represent a simple phenomena like three people sitting around a square table fig 87, the introduction accurate illumation makes it harder to clarify borders between objects, as in figure 232), and the artist must overcome them.

Aesthetics then becomes not a matter of taste, but of effective solutions to problems.

Similarly, our visual perception can be thought of as a narrative in which our perceptive mechanisms solve the problems presented to them by eyesight. HOW our mechanisms solve the problems is subject to debate. There are behaviorist theories. There are blah blah blah theories. And then there are the Gestalt Theories, which are moving in that they are the most effective. According to Gestalt theory, we solve the problems of resolving visual information according to the law of simplicity. So that a given shading, or a given light patch will be interpreted as illumination IF that organization produces the percept of greatest simplicity.

All this is a development of Arhneim's stated desire at the beginning of the book to depict the visual perception of art as a dynamic, and not a receptive, act.

How shading works

First of all, I was totally amazed by how Livingstone breaks down the artistic dilemma of having to visually portray differences in luminance through art using tools that cannot even approximate the number of luminances in the natural world. Furthermore, our visual system cannot even signal the scope of these different luminances, so we must rely on center/surround organization that discriminates locally. Thus, we see the abrupt differences between how dark/light something is and its immediate surround. In order to achieve this effect in artwork, artists use chiaroscuro by creating subtle opposing gradations in luminance between foreground and background The very idea of creating an artistic representation of something that cannot be accurately produced, which is in turn seen through a visual system that cannot biologically handle that difference in luminance is fascinating (and quite vexing).

I also really liked Livingstone's discussion toward the end of the chapter on how color and luminance was stretched by modernist and impressionist painters such as Monet, Matisse, and Derain. These paintings seem visually accurate, however, because the luminance values create depth cues that are easily perceivable. There is something of a dissonance in these paintings, as one aspect seems entirely realistic whereas another is not readily comprehendible. For Monet, Livingstone posits that the colorblind Where system detects the overall shape and spatial organization that creates depth, though the low-luminance contrasts also keep the viewer from being able to clearly or immediately identify the objects (What system). In the Monet example here and in Derain's work, aspects of the What system may create expressive rather than realistic dimensions while preserving the (colorblind) accuracy of depth.

Michelangelo mixed the pigments in the highest contrast to create consistently realistic luminance, thus producing an artful three dimensionality on a two dimensional canvas. Looking at the images in Livingstone, one print of the original and one of the black and white, it’s really impressive to see how unmistakable and clear the shading is. “Luminance is necessary to perceive depth,” which is clearly what Michelangelo was striving for and accomplished quite successfully. Trying to achieve depth and three dimensionality made me think of Mondrian’s striving for a perfectly flat, two-dimensional image. However, he did seem to use pure colors, which have varied luminance. Brightness distribution over the whole visual field helps to orient objects in space. So a large, bright red section might seem much farther forward than a small blue square underneath it. Also, the local schematic would have impacted the changes in luminance, thus creating the perception of depth.

Our visual systems are able to process thousands of luminance levels with a finite number of excitatory cells. Because of the center/surround organization of the retinal ganglion cells and the thalamic cells, they respond to abrupt changes, in this instance, in changes of luminance. The visual system organizes brighter areas and darker areas in each area of the painting, rather than constructing an entire gradient from the whole visual field. Rembrandt was able to successfully manipulate luminance by creating gradual shifts in the background and using sharp local changes to increase contrast. Similarly, Daddi used luminance changes to enhance the throne, painted in perspective. The alternating lights and darks and highlights make the curvature of the seat perceivable.

Arnheim’s discussion of the location of the light source, either inside or beyond the painting, was interesting. The idea of the objects “becoming enlightened” by way of contact with the light source was really intriguing. Bringing the viewer’s attention to significant objects without throwing off the balance or meaning of a piece can be a tricky process. But in The Holy Family, Rembrandt uses lights and shadows to create a dynamic piece. The “glowing” book seems to make no sense until Joseph’s gigantic shadow lends to the location of the light source. In addition, that the illuminated book and the pale pink cherubs in the top left corner both stand out against dark shadows. Mary’s face is also brighter as it is caught between the reflections of the angels and the (good) book.

I've just finished a painting that I adapted from a black and white photograph. As you all know, a

B &W photograph can have some confusing shadows, especially if you're trying to paint them in color. I too am guilty of undermining the importance of shadows, but I have to say that once I added ( what I thought was going to be a big reddish black mistake) the arm it was on and the microphone it was from seemed to pop! It all came to life and started to look like a real painting.

Shadows and Light

It was difficult separating my interest in architecture from Arnheim’s chapter of Light, since light and shadows play such a significant part in the experience of architecture. And I find it interesting that Arnheim distinctly notes that while light is prominent in causes of visual perception, light is “more than just the physical cause of what we see…it is the most fundamental and powerful of human experiences.” And this is precisely where light fits into architecture—it is not simply an object, although the unveiling aspect of light does reveal a surfacing of texture, depth, and form of a space, but foremost it is towards an experience. It is fascinating how the energy of a space can become diminished or sustained through the blending of light and shadows and we feel it perhaps most poignantly in our childhood homes. For example, the light which marks the interior of the home is simultaneously cozy and remote which is in part due to the contrasting darkness. Void and presence, interior and exterior, become part of the bodily experience and through this blending of light, a room is transformed into an embodied, sensory place. Demonstrating quite clearly this ‘phenomenon’ is the opening pages of Proust’s Swann’s Way, in which the narrator is desperately trying to fall asleep against the disorientating effects of shadows, “ But my sadness was only increased by this since the mere change in lighting destroyed the familiarity which my bedroom had acquired for me (9).” The lighting of homes offers profound experiences and I find it truly uncanny walking in residential neighborhoods at night when rooms becomes visible through illumination. Not only do you see the depth and texture of a room but you see where the shadows creep and fall.

But what happens when we lose our confidence in the mystery and depth of shadows? Like the sculpture Arnheim noted in the modern museum galleries, architectural spaces also become “murdered” by a flooding of illumination. Depth created by shadows projects a qualitative dimensionality to space, which establishes itself as distinct from the geometry of a given place. In turn, the converging of geometrical properties and lighting create an environment, which affects the entire body experience. However, in spaces that are flooded by light, for example office cubicles and classrooms, the play of depth and texture become paralyzed and erased of all diversity. In work places such as these, shadows are deemed inefficient to the atmosphere of production. It is no wonder that people working in such places are unhappy! As Arnheim noted, light gives form but in aggressively lighted spaces, appearances are forced without form. Without form, without texture, and without shadows which lead us into place, the site disembodies and disturbs the relation between body and architectural space.

shadows and matisse

I really enjoyed the Livingstone reading for this week. Having all of those images makes what she is saying so much easier to understand, and I find it much more easy to concentrate on than Arnheim. I liked the way she began by saying simply that our default assumption is that the light source is coming from above, and the simple shading examples she gave (the spheres) were fantastic - I kept turning my book upside down over and over. I don't know much about art from before the renaissance, but I could easily see what Livingstone was talking about when comparing the images in the chapter -- earlier artists tried to achieve a wider range of luminanace by adding white to some pigments, and after reading it it kind of makes sense why they looked so choppy and disjointed to me.


I especially enjoyed the Matisse images at the end of the chaper, after reading about the poor reaction of Monet's work it reinvigorated me to see Matisse's bright colors and fascinating exploration. I couldn't help looking up more and more of his portraits.

The part of the Arnheim reading that I found the most interesting was the section on shadow. I typically take them for granted, but they are a huge part of some people life. I am not sure if I agree, however, with the way that he thinks about attached and cast shadows. I agree that attached shadows are an integral part of the object and can be seen as an outgrowth of the object, but it also is the one that some people take the least notice of. And I don't think I agree that cast shadows are always an imposition/interference. Unless I misread it and he is referring only to some types of art? Because I do not think that is true in everyday life, and not in art because there are many types of art that have beautiful cast shadows.

short example

Finally after all this time I think we can start to talk about artist’s intent. Color, shape, and object placement can convey a certain something, however light, as Arnheim points out, is one of the most active informational sources in our life, Light is easily taken for granted in our day to day existence, as we perceive it to be everywhere and when it is not or in limited supply with see not the absence of it but another incarnation of seeing. By using this information artists can manipulate most effectively the gaze and attention of the viewer.

While in the Uffizi this break I came across a Parmigianino I have always admired “Madonna With the Long Neck”. My particular attraction to it stems from Modigilani who I was exposed to at a young age citing a similarity in the long necks of his female subjects and my long neck ( I think my dad was trying to make me feel normal, which I did, so the whole mission was a little weird).



Parmigianino uses a very basic light source from the top right to selectively highlight in order of religious importance: the Christ child, the Madonna, and then the on-lookers and background information. The child’s bright pale body is seen as brighter because it lacks intense detailing as opposed to the Madonna’s clothing, which is highly textured revealing the form of her body. In this instance Parmigianino uses the light’s interaction with the fabric to create and human form beneath her holy garb, but also to keep the viewer interested in her figure, as it seems that the theme of this painting is merely a vehicle for his interpretation of Madonna. The light that falls of her breast brings the viewers eye back to her extremely long fingers and then to her neck, both so elegant that one almost forgets that Christ is glowing happily in her lap. The light, however, does not land with any particular brightness on her face- instead in seems to pool on her chest and lap. This creates a circular focus of light, the heaviest part of the pool is with out a doubt Christ but his luminance brings the viewer back around again and again to Parmigianino’s realization of the Madonna. His use of light to focus the viewer on his technique seems to be a play on the his general style which is one of manipulated fancy, sometimes with light, sometimes with shape, and sometimes, with view point.

Light and Shadow

Arnheim’s discussion of how children and early art use outlines, local brightness, and local color reminded me of the difficulties I experienced when I learned how to shade drawings. For years and years, despite the many lessons I was given in shading, I refused to apply them to my own work. Rather than adding depth to the images, I felt that shading a face simply made it look dirty. Dramatic changes in brightness values, like clothing or hair or eyes would be a different color, but anything that is theoretically the same shade all over, such as skin, was left blank. In hindsight, I wonder why I thought these uniform figures were more realistic than the “dirty” shaded ones. I don’t think it was a matter of my shading being wrong. I didn’t learn any new techniques or have any major breakthroughs before I began to apply it to my work. I honestly think it must have been a difference in perception. What that difference is, I can’t begin to say, but the way I saw the world changed once I began to think of images in terms of shadows and light.

On a related note, the idea that light creates depth is not new to me, but it is one that I have always found fascinating. That, given the right lighting, a three dimensional object like the cone that Arnheim discusses (311) can appear to be two dimensional is hard to imagine. Logically, it seems like all three dimensional objects should remain that way and should be easy to perceive in their true form. Yet, in light of how much time and energy is spent on making two dimensional objects look like they exist in space, it should not be so surprising that the reverse is possible. It just emphasizes how easy it is to trick our brains into believing one thing about an image when the reverse is actually true.

Finally, I loved Arnheim’s discussion of cast shadows, particularly his description of the tribesmen in western Africa who “avoid walking across an open space or clearing at noontime because they are afraid of ‘losing their shadow’” (317). The idea that a shadow is an extension of the person it belongs to has always been interesting to me (and just might have stemmed from my childhood love of Peter Pan…), so the idea that the process of a shadow shrinking as the sun gets further and further overhead is actually a manifestation of it getting weaker is intriguing. In fact, now that I think of it, the tendency to see a shadow as separate from the object it belongs to just might explain the absence of shading in early art. If a person believes that cast shadows are separate from objects and people, the idea that other shadows are an integral part of the person or object itself would be hard to grasp.

Chasing Light

Arnheim (1974) writes, “But the prevailing view throughout the world seems to have been and to be that light, although originally born from primordial darkness, is an inherent virtue of the sky, the earth, and the objects that populate them, and that their brightness is periodically hidden or extinguished by darkness” (p.304). Thus, mentally light’s ownership is given to the object (material or abstract) that reflects it. This suggests that light is not an entity in itself but rather a property of something else. Arnheim (1974) explains that only in the 20th century has disembodied light become a subject worthy of artistic consideration.

James Turrell has taken up the challenge to tackle light as an artistic subject, rather than a property or agent of the visual scene. In his work, Turrell explores the behavior of light and plays with human perception on a fundamental level. The following light projection, or more appropriately sculpture, exemplifies the illusory qualities of Turrell’s work.



What follows is an attempt to understand how Turrell creates a 3-dimensional mass of light. Perhaps someone can chime in with a theory or further insight? This is what I have so far: Turrell is able to create the shape of a wedge using projected light. Livingstone (2002) explains that luminance contrast creates a sense of depth. Turrell applies this principle when constructing the wedge or jukebox like structure. When converted to grayscale the viewer can see that the wedge is much brighter than the background area and as a result, juts out from the wall.



The points at which the wall and floor meet in the background create two distinct perpendicular lines that the viewer mentally continues behind the foreground mass. Additionally, the mass is translucent and as a result the bottom of the mass has a lower luminance grade than the portion of the mass resting on the wall. Interestingly the edges of the wedge touching the floor and wall appear brighter than the rest of the wedge. It may be that the phenomenon is a property of the photograph, not the sculpture. However if it is not (and I think this is likely), the visual effect suggests that more light is being pressed into the corners of the sculpture, like mini-congregations of light. Perhaps this is the result of an exaggerated luminance contrast. The edges appear brighter because in relation to the wall and floor they are. Arnheim (1974) summarizes this phenomenon: “Whether or not a handkerchief looks white is determined not by the absolute amount of light it sends to the eye, but by its place in the scale of brightness values provided by the total setting” (p.306).

The question remains if Turrell was successful at treating light as an independent body. Although he has manipulated light as a subject it is debatable as to whether he has freed light from the bounds of a material concept. In the above description I unintentionally referenced Turrell’s treatment of light as a wedge, jukebox, mass that has a luminance value. I conformed to Arnheim’s stereotype—light is a property of an object, not an object in its own right. Thus I remain at a loss as to how to conceive of light as anything other than a visual attribute. As I wrote the previous sentence I thought of the treatment of “Tinkerbell” in Peter Pan and how she is sometimes represented as a moving light. Perhaps this is the answer—light must be given life.

On a final note, and returning to the quotation referenced in the beginning, Arnheim (1974) argues that we conceive of light as an internal property of an object that projects outwards. Darkness is created by the blockade of light. In the sculpture below Turrell experiments with this notion, in it, the inverted pyramid is reflected on the ground. What would be the pyramid’s shadow is not darkness, but rather light. This gives the appearance that the pyramid is radiating light, rather than simply reflecting it. In contrast, the viewer could interpret the pyramid as being in the spotlight, and thus a witness to light. Either way, the origin of light is falsified.