How We See

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Light

(Please note: I have used several resources to gather this information.)

Light is the energy that our eyes detect when we see. When there’s no light, we won’t be able to see anything. Light may differ in color, brightness and purity. Color, or hue, is dependent upon the wavelength of light. Low-frequency light, or light with longer wavelengths, is reddish; while high-frequency light, or light with shorter wavelengths, is bluish. The brightness of light, on the other hand, is measured by the wave’s amplitude (or height). High-amplitude light waves are brighter than low-amplitude light waves. Lastly, purity or saturation is measured by the amount of white light added. Pure light has lesser added white light than saturated light. The Color Tree is oftentimes used to demonstrate the different properties of light. Hue moves around the tree; saturation goes outward; and brightness moves upward.

How we see

There are many different parts of the eye that help to create vision. Light passes through the cornea, the clear, dome-shaped surface that covers the front of the eye. The cornea bends – or refracts – this incoming light. The iris, the colored part of the eye, regulates the size of the pupil, the opening that controls the amount of light that enters the eye. Behind the pupil is the lens, a clear part of the eye that further focuses light, or an image, onto the retina. The retina is a thin, delicate, photosensitive tissue that contains the special “photoreceptor” cells that convert light into electrical signals. These electrical signals are processed further, and then travel from the retina of the eye to the brain through the optic nerve, a bundle of about one million nerve fibers. We “see” with our brains; our eyes collect visual information and begin this complex process.

Perceiving Visual Dimensions: Perceiving Shape

We perceive shapes through the help of contours and patterns. A contour is where a sudden change in brightness occurs. For example, we perceive cylinders because we observe that the left and right sides gradually diminish in brightness. Patterns, on the other hand, are used for organizing perceptions. Gestalt Psychology underscores that the whole is not equal to the sum of its parts. (Note: “Gestalt” is German word for “form” or “configuration”.) Common principles of gestalt psychology as applied in shape perception are figure-ground relationship, closure, proximity and similarity. Figure-Ground Relationship means that we perceive shape by identifying what is figure and what is ground, and by comparing them with each other. Closure is filling the spaces of disconnected and incomplete figures. This means that an incomplete circle will still be perceived as a circle because we naturally close the missing gaps together to form a shape. Proximity and Similarity are principles of grouping. Proximity is grouping by closeness, while similarity is grouping by sameness. For example, a spiral is formed by grouping circular lines in proximity, or a flower may be formed by similarity in a cross stitching.

Perceiving Depth

We perceive depth through the help of binocular and monocular cues. Binocular cues come from the disparity between the left and the right eyes. Because the left and the right eyes naturally record different visual sensory information due to their location, the brain then processes two different images to provide meaning on the depth of visual objects. On the other hand, monocular cues are those provided by a single eye. They are also known as pictorial cues because artists apply them to mimic a 3-dimensional image to a 2-dimensional platform. This is why we perceive depth even if the canvas is flat.

Monocular cues, such as familiar size, height in field of view, linear perspective, overlap, shading and texture gradient, allow us to perceive depth with a single eye.

  • Familiar size comes from experience. We know for certain that buildings are taller than cars from experience.
  • Height in Field of View means that objects placed in higher position are perceived to be farther. This is the reason why we perceive the size of the moon differently with different locations. Because we do not have familiar experience over its actual size, we perceive the moon as farther and smaller when above us than when it is near to the horizon.
  • Linear Perspective means that far objects take less retina space, so we perceive converging lines as farther than parallel lines.
  • Overlap means that the concealing object is closer than the concealed object. Shading makes use of lighting and object location.
  • Texture Gradient means that objects with denser and finer texture are farther than objects with lighter and thicker texture. Cartoonists oftentimes use texture gradient to provide depth in their drawings.