The architecture of light: architectural lighting design concepts and techniques. A textbook of procedures and practices for the architect, interior designer and lighting designer pdfdrive com

Figure 5.5 The interactions of light are always about the basic unit of light: The Lumen.

Chapter 6 Physiology of Vision

Figure 6.1 The major components of the human
The human eye, with all of its mechanics, deserves a heavy book of its own. But, for our purposes we will focus on the components of the eye that detect and translate light. These components initiate the chemical process that transmits information to our brain, where it is processed into visual experience. To study these mechanics as designers, we must understand what the eye and brain need to perform and feel comfortable in an environment.
To better understand the needs of our visual system, we start by studying
some mechanical basics that we touched on earlier.
Adaptation
This term is the name we give to the mechanics of the eye and brain working to control the amount of light that enters the eye and is translated by the brain. We “dark adapt” when we walk into a dark room, as the mechanics of our eyes and brains work to make the most of what little light is available. “Bright adaptation” occurs when we transition into a brighter space and our eyes and brains work to limit the amount of light entering the visual system. Adaptation
occurs unconsciously. It is worth knowing that bright adaptation happens rather quickly. Dark adaptation can take a few minutes to occur completely. For this reason, we give extra thought to light levels when we transition people from
Figure 6.2 The flexible “crystalline lens” changes shape to refract light differently as the eye focuses on objects that are far away (left) or near (right).
bright spaces to dark spaces.
Accommodation
This is a fancy name for the ability of the eye to focus on objects at different distances. The eye has flexible refracting components that change shape to bend light differently when we shift focus from a close object to an object far away.
STRUCTURE OF THE EYE
The human eye consists of a number of impressive components that perform all of these complex tasks. Nearly all of these functions can be understood by finding analogy with a camera.
The outermost
component of the eyeball is the cornea, a fluid-filled bulge at the front of our eye that does a fair amount of gathering and focusing of light towards the back of the eyeball. The cornea also does a wonderful job of protecting the other components of the eye and filtering out harmful radiation.
Behind the cornea is
the iris. The iris is the component of the eye that carries “eye color” and acts as
a shutter device, opening and closing to control the quantity of light that enters the eyeball. It is the iris that is first to act when the visual system “adapts” to different light levels. The pupil is the name for the aperture that the iris creates. So we see our pupil change in size to admit more or less light as conditions change.
Behind the pupil is the flexible, shape-changing lens that is responsible
for a small, but critical, portion of our accommodation (focusing). This lens is attached to muscles that contract and relax to optimize the shape of the lens to refract light from far away or from nearby as we focus on objects at different distances.
All of these components are working in harmony at all times to deliver the
ideal quantity of light to the elements at the back of our eyeball. These elements make up the retina. The retina is home to all of our light-detecting photoreceptors called rods and cones. The different types of photoreceptors are distributed in a very purposeful way that can be broken down into three areas of interest.
The periphery of our retina is home to photoreceptors called “rods” that detect low levels of light.
The central area of our retina is called the macula and is home to a mix of rods and our more detail oriented photoreceptors called “cones.”
The very center of our retina is called the fovea, and it is home exclusively to cones. Because cones are so critical for translating detail and color, the fovea is slightly concave to maximize the surface area available. The density of cones at the fovea allows for greater detail and color perception at the center of the field of vision. It is this center most area of the retina towards which all of the other mechanics of the eyeball are working to direct light.
The cones and rods are the critical light detecting components of the eye.
To understand how the two different systems work to contribute to vision in different light situations, we will expand on them here.
Rods
Rods are the photoreceptors that populate the outer perimeter of the retina and are responsible for our so-called “peripheral vision”