C haptEr 9 design Environments and systems
340
of various wavelengths originally present in the light source being
subject to subtraction via the absorption or transmission of specific wavelengths by the material itself. A white light shining on
an opaque tent surface that absorbs the blue wavelength will cause
the surface to appear yellow, since red and green wavelengths will
be reflected and together these appear yellow. If a light source with
wavelength in the green spectrum acts on the surface, the surface
will appear green. It would also appear green if cyan (green and
blue) shined on it. On the other hand, a light source of blue wavelength only shined on the surface would cause the tent surface
to appear black, since the impinging blue wavelengths would be
absorbed by the material. Interesting phenomena can result. Thus,
a specular sphere that appears black can have a white highlight, or a
sphere that appears to generally be one color can have reflections of
a different color, depending on the wavelengths present in the original light source and the absorptive characteristics of the material.
The term pigment (most commonly associated with paints) is used to
describe a material that absorbs a single wavelength or color of light.
Many nanomaterials are now found in pigments used in paints. The
color descriptor of a pigment is the complementary color of the color
absorbed by the pigment. If a pigment on a tent material has red,
green, and blue shining on it and absorbs blue only, it is referred
to as being a yellow pigment (since red and green—or yellow—
are reflected and hence seen). A red pigment on the same surface
would absorb cyan (blue and green) and appear red. If a yellow
light (having red and green only) were to shine on a blue pigment,
the surface would appear black, since the blue pigment absorbs red
and green. In relation to common paints and other coatings, actual
pigments are normally not pure pigments that absorb only single
wavelengths. A material that is either transparent or translucent not
only selectively reflects and absorbs wavelengths from a light source
shining on it but also transmits particular wavelengths.
visual perception
The basic physics of light and color are one thing, but the way
humans actually perceive, understand, and are affected by light
and color are strongly affected by both the overall context in which
something is seen and fundamental “eye–brain” neurological
responses in which vision is a complex part of the human sensory
system. These are vast subjects that are simply beyond the scope of
this text. Only a few salient points are noted here, simply to give a
flavor of the issues important to our discussion.
340
of various wavelengths originally present in the light source being
subject to subtraction via the absorption or transmission of specific wavelengths by the material itself. A white light shining on
an opaque tent surface that absorbs the blue wavelength will cause
the surface to appear yellow, since red and green wavelengths will
be reflected and together these appear yellow. If a light source with
wavelength in the green spectrum acts on the surface, the surface
will appear green. It would also appear green if cyan (green and
blue) shined on it. On the other hand, a light source of blue wavelength only shined on the surface would cause the tent surface
to appear black, since the impinging blue wavelengths would be
absorbed by the material. Interesting phenomena can result. Thus,
a specular sphere that appears black can have a white highlight, or a
sphere that appears to generally be one color can have reflections of
a different color, depending on the wavelengths present in the original light source and the absorptive characteristics of the material.
The term pigment (most commonly associated with paints) is used to
describe a material that absorbs a single wavelength or color of light.
Many nanomaterials are now found in pigments used in paints. The
color descriptor of a pigment is the complementary color of the color
absorbed by the pigment. If a pigment on a tent material has red,
green, and blue shining on it and absorbs blue only, it is referred
to as being a yellow pigment (since red and green—or yellow—
are reflected and hence seen). A red pigment on the same surface
would absorb cyan (blue and green) and appear red. If a yellow
light (having red and green only) were to shine on a blue pigment,
the surface would appear black, since the blue pigment absorbs red
and green. In relation to common paints and other coatings, actual
pigments are normally not pure pigments that absorb only single
wavelengths. A material that is either transparent or translucent not
only selectively reflects and absorbs wavelengths from a light source
shining on it but also transmits particular wavelengths.
visual perception
The basic physics of light and color are one thing, but the way
humans actually perceive, understand, and are affected by light
and color are strongly affected by both the overall context in which
something is seen and fundamental “eye–brain” neurological
responses in which vision is a complex part of the human sensory
system. These are vast subjects that are simply beyond the scope of
this text. Only a few salient points are noted here, simply to give a
flavor of the issues important to our discussion.