Depth

Spatial Effects in Form Interrelationships
Detachment, touching, overlapping, penetration, union, subtraction, intersection, or coinciding of forms-each kind of interrelationship produces different spatial effects.

In Detachment. Both forms may appear equidistant from the eye, or one closer, one farther away.

In Touching. The spatial situation of the two forms is also flexible as in detachment. Color plays an important role in determining the spatial situation.

In Overlapping. It is obvious that one form is in front of or above the other.

In Penetration. The spatial situation is a bit vague, but it is possible to bring one form above the other by manipulating the colors.

In Union. Usually the forms appear equidistant from the eye because they become one new form.

In Subtraction. As well as in penetration, we are confronted with one new form. No spatial variation is possible.

In Coinciding. We have only one form if the two forms are identical in shape, size, and direction. If one is smaller in size or different in shape and/or direction from the other, there will not be any real coinciding, and overlapping, penetration, union, subtraction, or inersection would occur, with the possible spatial effects just mentioned.

[Wong, Wucius. Principals of Two-Dimensional Design. New York: Van Nostrand Reinhold Company, 1972.]

Qualities
We must digress again to consider psychological qualities ordinarily taken for granted, even by artists. European art from the later years of the Middle Ages to well into the last century depended greatly on the artist's ability to achieve depth by various orderings of line, shape, value, color, and texture on a flat surface, wall, board or canvas. No wonder the elaborate picture frame became so important in time: it served to isolate the painting and establish it as a kind of window upon ever-deepening landscape space. But there is nothing in any of these elements to suggest that either deep or shallow space will be the result of their use. However, the moment they are put down with great skill and knowledge of optics, or even thrown down--two or three lines or shapes, two or more colors or values (strong and weak, warm and cool, dark and light), rough and smooth textures--the viewer will have some undeniable experience of advancing and receding parts.

Arnheim, accepting a suggestion made by James J. Gibson in his book The Perception of the Visual World (1950), says that "three-dimensional space is created by perceptual gradients." He describes these as the "gradual increase or decrease of some perceptual quality in space or time. For example, oblique parallelograms contain a gradient of location, in that the slanted figure lies at an evenly changing distance from the normal axes of the horizontal and vertical." Even a single oblique line contains a gradient of location or distance in relation to the implied horizontal and vertical axes (repeated in the sides and top and bottom of a square or rectangular format). A series of lines or shapes, wherein the elements diminish in height or width, contains a gradient of size. If the intervals of space between these elements grow narrower or wider, they too contain a gradient of size. The other gradients are those of value (light-dark gradient) and texture (smooth-rough gradient); still another pertains to sharpness/dullness or firm/fuzzy qualities.

Gradients...... are not dependent on anything seen in nature or the world; they pertain entirely to illusionary space, whether used to depict anything or not. The flat surface is forced to yield so that the eye may achieve order in depth.

[Harlan, Calvin. Vision & Invention, An Introduction to Art Fundamentals. Englewood Cliffs, NJ: Prentice-Hall, 1986.]

Spatial Gradation
Spatial gradation affects the shape or the size of unit forms. The relationship between the unit forms and the picture plane is never constant.

Two kinds of spatial gradation can be distinguished:
1) Spatial Rotation. With gradual diversion from the picture plane, a unit form can be rotated so that we see more and more of its edge, and less and less of its front. A flat shape can become narrower and narrower until it is almost a thin line. Spatial rotation changes the shape of a unit form.

2) Spatial progression. This is the same as the change of size. Increase or decrease of the size of unit forms suggests the forward or backward progression of unit forms in space. The unit forms are always parallel to the picture plane, but they may appear far behind the picture plane when it is small, or even in front of the picture plane when it is large.

[Wong, Wucius. Principals of Two-Dimensional Design. New York: Van Nostrand Reinhold Company, 1972.]

C O N S I D E R:

Dimension

Downward

Horizonatally Inward

Quality

Condition

Mode

Complexity

Obscurity

Gravity - Seriousness

Intensity - As in silence or color

Emotional profundity

Farthest

Innermost

Extreme part or state

Space

Place

State

Recondite, mysterious, obscure

Sagacious, wise, profound, shrewd

Depth Perception [The Following text is from: Coon, Dennis. Introduction to Psychology, Exploration and Application. St. Paul: West Publishing Company, 1989, the chapter on Perceiving.]

I N D E X: Depth perception - Is Depth Perception Learned? - Depth cues [Monocular cues, Binocular cues] - Muscular Cues [Accommodation, Convergence] - Stereoscopic Vision [Retinal disparity, Random dot stereograms] - With one eye - Pictorial Depth Cues [Linear perspective. Relative size. Light and shadow, Overlap/interposition, Texture gradients, Aerial perspective, Relative motion/ motion parallax] - Pictorial depth cues are not entirely universal - How do the depth perception cues relate to daily experience? [Apparent distance, The apparent distance hypothesis]

T E X T
Depth Perception.
Depth perception is the ability to see three-dimensional space and to accurately judge distances. Without depth perception, you would be unable to successfully drive a car or ride a bicycle, play catch, shoot baskets, thread a needle, or simply navigate around a room. The world would look like a flat surface.

A. Is depth perception learned? Some psychologists (nativists) hold that depth perception is inborn. Others (the empiricists) view it as learned. Most likely, depth perception is partly learned and partly innate. Some evidence on the issue comes from work with the visual cliff. The visual cliff is basically a glass-topped table. On one side a checkered surface lies directly beneath the glass. On the other side, the checkered surface is 4 feet below. This makes the glass look like a tabletop on one side and a cliff, or drop-off, on the other.

To test for depth perception, 6- to 14-month-old infants were placed in the middle of the visual cliff. This gave them a choice of crawling to the shallow side or the deep side. (The glass prevented them from doing any "sky-diving" if they chose the deep side.) Most infants chose the shallow side. In fact, most refused the deep side even when their mothers tried to call them toward it (Gibson & Walk, 1960).

Other tests have shown that human depth perception consistently emerges at about 4 months of age (Aslin & Smith, 1988). And tests show that babies first become aware of "3-D" designs at age 4 months. The nearly universal emergence of depth perception at this time suggests that it depends more on brain development than it does on individual learning. It is very likely that at least a basic level of depth perception is innate.

A number of depth cues combine to produce our experience of three-dimensional space. Depth cues are features of the environment and messages from the body that supply information about distance and space. Some cues will work with just one eye ( monocular cues), while others require two eyes, ( binocular cues).

l. Muscular Cues. Muscular cues come from within the body. Such as:
Accommodation, a monocular cue for depth perception. The lens in each eye must bend or bulge to focus nearby objects. Sensations from muscles attached to the lens are channeled back to the brain. Differences in these sensations help us judge distances within about 4 feet of the eyes. Beyond 4 feet, accommodation has a limited effect on depth perception.

Convergence, a second bodily source of information about depth, a binocular cue. When you look at a distant object, the lines of vision from your eyes are parallel. However, when you look at something 50 feet or less in distance, your eyes must converge (turn in) to focus the object. Whenever you estimate a distance under 50 feet (as when you approach a stop sign, play catch, or zap flies with your personal laser), you are using convergence. There is a relationship here between muscle sensations and distance. Convergence is controlled by a group of muscles attached to the eyeball. These muscles feed information on eye position to the brain to help it judge distance. You can feel convergence by exaggerating it: Focus on your fingertip and bring it toward your eyes until they almost cross. At that point, you can feel the sensations from the muscles that control eye movement.

2. Stereoscopic Vision. The most basic source of depth perception is:
Retinal disparity, also a binocular cue. Retinal disparity is based on the simple fact that the eyes are about 2 1/2 inches apart. Because of this, each eye receives a slightly different view of the world. When the two images are fused into one overall image, stereoscopic vision occurs. This produces a powerful sensation of depth. And, retinal disparity can be used to produce 3-D movies by filming with two cameras separated by several inches. Later, both images are simultaneously projected on a screen. Audience members wear glasses that filter out one of the images to each eye. Since each eye gets a separate image, normal stereoscopic vision is duplicated. Perceiving depth is more than a simple blending of two images, or "pictures," of the world:

Random dot stereograms. Notice that two squares of random dots contain no lines, edges, or distinct patterns. Just the same, wen these random dot stereograms are properly viewed (one to each eye), a center area seems to float above the background. Researcher Bela Julesz believes the designs show that the brain is very sensitive to any mismatch of information from the eyes. In this example, depth comes from shifting dots in the center of one square so they do not match dots in the other square (Julesz, 1971; Ross, 1976). To a large extent, three-dimensional space is woven from countless tiny differences between what the right and left eyes see.

If disparity is so important, can a person with one eye perceive depth? A one-eyed person lacks convergence and retinal disparity, and accommodation is helpful mainly for judging short distances. This means that a person with only one eye will have limited depth perception. Try driving a car or riding a bicycle some time with one eye closed. You will find yourself braking too soon or too late, and you will have difficulty estimating your speed.

Pictorial Cues for Depth. A good movie, painting, or photograph can create a convincing sense of depth where none exists. And, as noted, a one-eyed person can learn to accurately gauge depth. How is the illusion of depth created on a two-dimensional surface, and how is it possible to judge depth with one eye? The answers lie in the pictorial depth cues, all of which are monocular (they will work with just one eye). These cues supply much of the information present in real three-dimensional scenes (Haber, 1980). To understand how the pictorial cues work, imagine that you are looking outdoors through a window. If you traced everything you saw through the window onto the glass, you would have an excellent drawing, with convincing depth. If you then analyzed what was on the glass, you would find the following features:

Pictorial Depth Cues. When combined, they can create a powerful illusion of depth.
[NOTE: The visuals in the original text are not included here.]
l. Linear perspective. This cue is based on the apparent convergence of parallel lines in the environment. If you stand between two railroad tracks, they appear to meet near the horizon. Since you know they are parallel, their convergence implies great distance.

2. Relative size. If an artist wishes to depict two objects of the same size at different distances, the artist makes the more distant object smaller. Films such as Star Wars and Return of the Jedi created sensational illusions of depth by rapidly changing the image size of planets, space stations, and starships.

3. Light and shadow. Most objects in the environment are lighted in ways that create clear patterns of light and shadow. Copying such patterns of light and shadow can give a two dimensional design a three-dimensional appearance.

4. Overlap. (Also known as interposition ) . It is a depth cue that occurs when one object partially blocks another object. Hold your hands up and have a friend try to tell from across the room which is nearer. Relative size will give the answer if one hand is much nearer to your friend than the other. But if one hand is only slightly closer than the other, your friend may have difficulty--until you slide one hand in front of the other. Overlap then removes any doubt.

5. Texture gradients. Changes in texture also contribute to depth perception. If you stand in the middle of a cobblestone street, the street will look coarse near your feet. However, its texture will get smaller and finer if you look into the distance.

6. Aerial perspective. Smog, fog, dust, and haze add to the apparent distance of an object. Because of aerial perspective, objects seen at great distance tend to be hazy, washed-out in color, and lacking in detail. This is true even in clear air, but it is increasingly the case in our mechanized society. As a matter of fact, aerial haze is often most noticeable when it is missing. If you have traveled the wide open spaces of states such as Colorado or Wyoming, you may have seen mountain ranges that looked only a few miles away, and then were shocked to find that you were actually viewing them through 50 miles of crystal-clear air.

7. Relative motion. Relative motion, also known as motion parallax , can be seen by looking out a window and moving your head from side to side. Notice that objects near you appear to move a sizable distance as your head moves. In comparison, trees, houses, and telephone poles at a greater distance appear to move slightly in relation to the background. Distant objects like hills, mountains, or clouds don't seem to move at all. Not really a pictorial cue except in movies, television, or animated cartoons. However, wen it is present, depth is almost always perceived. Much of the apparent depth of a good movie comes from the relative motion of objects captured by the camera. People who can only see with one eye depend heavily on motion parallax. Often, they make frequent head movements to exaggerate parallax and improve depth perception.

Pictorial depth cues are not entirely universal. Some cultures use only selected pictorial cues to represent depth. People in these cultures may not easily recognize other cues (Deregowski, 1972). For example, researcher William Hudson tested members of remote tribes who do not use relative size to show depth in drawings. These people perceive simplified drawings as two-dimensional designs. They do not assume, as we do, that a larger image means that an object is closer.

How do the depth perception cues relate to daily experience? Like the bodily depth cues, we constantly use the pictorial cues to gauge depth and judge distances. Cues of both types also combine to produce an intriguing illusion. When the moon is on the horizon, it tends to look as large as a silver dollar. When it is directly overhead, it looks like a dime, very much smaller than it did earlier the same evening. Contrary to what some people believe, the moon's image is not magnified by the atmosphere. If you take a photograph of the moon and measure its image, you will find that it is not larger on the horizon. But the moon looks larger when it's low in the sky. This is because the apparent distance of the moon is greater when it is near the horizon than when it is overhead. When the moon is overhead there are few depth cues around it. In contrast, when you see the moon on the horizon, it is behind houses, trees, telephone poles, and mountains. These objects add numerous depth cues, which cause the horizon to seem more distant than the sky overhead (Dember & Warm, 1980).

The apparent distance hypothesis. The moon will immediately appear to shrink when depth cues are eliminated. It is directly related to changes in accommodation (Iavecchia et al., 1983; Roscoe, 1985). Extra depth cues near the horizon cause the eyes to focus on a more distant point than they do when you look overhead. Such changes in accommodation appear to provide the brain with a "yardstick" for judging the size of images, including that of the moon.

[Coon, Dennis. Introduction to Psychology, Exploration and Application. St. Paul: West Publishing Company, 1989, the chapter on Perceiving]

R  E  F  E  R  E  N  C  E  S 

Deep [ME dep. OE déop; akin to Goth diup(s), OIcel djup(r), OHG tiof] -Syn. 10. recondite, mysterious, obscure. 17. sagacious, wise, profound, shrewd. -Ant. 1,7,12,17 shallow.

[Urdang, Laurence, ed. Random House Dictionary of The English Language. New York: Random House,1968.]

1 Deep adj [ME dep. fr. OE déop; akin to OHG tiof deep, OE dyppan to dip -more at Dip] [Bef 12c] 1: extending far from some surface or area; as a: extending far downward [a __ well] b[1]: extending well inward from an outer surface [a __ gash] [a deep-chested animal] [2]: not located superficially within the body [__ pressure receptors in muscles] c: extending well back from a surface accepted as front [a __ closet] d: extending far laterally from the center [__ borders of place] e: occurring or located near the outer limits of the playing area [hit to __ right field] f: thrown deep [a __ pass] 2: having a specified extension in an implied direction usu . downward or backward [a shelf 20 inches __] [cars parked three-deep] 3a: difficult to penetrate or comprehend: Recondite [__ mathematical problems] b: Mysterioius, Obscure [a __ dark secret] c: grave in nature or effect [in __est disgrace] d: of penetrating intellect: Wise [a __ thinker] e: Involved, Engrossed [__ in debt] f: chracterized by profundity of feeling or quality [a __ sleep]; also: deep-seated [__ religious beliefs] 4a of color: high in saturation and low in lightness b: having a low musical pitch or pitch range [a __ voice] 5a: situated well within the boundaries [a house __ in the woods] b: remote in time or space c: being below the level of the conscious [__ neuroses] d: covered, enclosed, or filled to a specified degree -usu. used in combination [ankle-deep in mud] 6: Large [__ discounts] 7: having many good players [a __ bull pen] -syn see Broad -in deep water: in difficulty or distress

2 Deep adv [bef 12c] 1a: a vast or immeasurable extent: Abyss b [1]: the extent of surrounding space or time [2]: Ocean 2: any of the deep portions of a body of water; specif: a generally long and narrow area in the ocean where the depth exceeds 3000 fathoms [5500 meters] 3: the middle or most intense part [the __ of winter] 4: any of the fathom points on a sounding line other than the marks

Depth n [ME, prob. fr. dep deep] [14c] 1a: [1]: a deep place in a body of water [2]: a part that is far from the outside or surface [the __s of the woods] [3]: Abyss2 b [1]: a profound or intense state [as of thought or feeling] [the __s of misery]; also: a reprehensibly low condition [hadn't realized that standards had fallen to such __s] [2]: the middle of a time [as winter] [3]: the worst part 2a: the perpendicular measurement downward from a surface b: the direct linear measurement from front to back 3: the quality of being deep 4: the degree of intensity [__ of a color]: also: the quality of being profound [as in insight] or full [as of knowledge] 5: the quality or state of being complete or thorough [a study will be made in __]

Depth of field [1911]: the ragne of distances of the object in front of an image-forming device [as a camera lens] measured along the axis of the device throughout which the image has acceptable sharpness

Depth perception n [ca. 1911]: the ability to judge the distance of objects and the spatial relationship of objects at different distances