Vision, Color, & Light Flashcards
Visual Thinking
In Ware’s model, visual thinking means something very specific. Visual thinking is the process for how we allocate our attention.
There are three basic steps in visual thinking:
You make an eye movement.
An image is projected onto your retina and you can scan it for patterns.
The image enters your working memory and if it’s useful to you then you give it your attention.
The Optics of an Image on the Retina
There’s an unlikely sounding quirk to this set up, which is that mechanically speaking, our eyes see everything upside down. That’s because the process of refraction through a convex lens causes the image to be flipped, so when the image hits your retina, it’s completely inverted.
Rene Descartes and the Bull’s Eye
Proved that images appear upside down on the retina in the 17th century by setting a screen in place of the retina in a bull’s excised eyeball. The image that appeared on the screen was a smaller, inverted copy of the scene in front of the bull’s eye.
More on How we See: The Fovea
Most of the 6 to 7 million cone photoreceptor cells in the eye that detect color are crowded within the fovea centralis at the center of the retina. At the periphery of your vision, you pretty much only see in black and white. yet we perceive a continuous, full-color image from edge to edge because the brain is able to extrapolate from the information it already has.
1604 Johannes Kepler
Gives us the modern idea that light comes from the sun and is then reflected from objects into the eye.
1672 Isaac Newton
He held a triangle piece of glass in a darkened room that had been outfitted with a pinpoint of light. This prism revealed that white light produced color when refracted thought the glass.
Is light a wave or a particle?
A wave bends (think sound waves or water waves). Light didn’t appear to do this leading Newton to tentatively conclude that light was produced by particles.
1802 Thomas Young
In 1802 Thomas Young suggests that light is formed by waves. This was based largely on his observation that when you see colors on a thin film of water or oil the colors vary systematically based on the thickness of the film. Young’s view were not popular-some even saw his rejection of Newton’s theories as sacrilegious.
1905 Albert Einstein
Einstein posited that light had both particle and wave qualities. He proposed that indivisible units of light energy (photons) move in a wavelike manner. He used mathematical formulas supported by theories of quantum mechanics to describe light’s wavelike and particle-like characteristics.
Electromagnetic Radiation
Light is created with electromagnetic radiation. You create electromagnetic radiation by heating up an object. For example, if you heat up a piece of metal it gives off shorter and shorter wavelengths until it reaches about 1000 degrees Fahrenheit. At that temperature it start to emit visible light. Note that in photo editing software, like Photoshop, you can set the white point and it is measured in terms of temperature. Incandescent light is created by heat.
How the Eye Works
- Light passes through the pupil
- The lens focuses the image onto the retina
- Photoreceptors containing light-absorbing chemicals generate a neural signal when they absorb light
- The neural signals pass toward the front of the eyeball to the ganglion cells
- The ganglion cells send their signals from the eye to the brain via the optic nerve
Diurnal Animals
Have pigment cells that absorb light which means that they need plenty of light to see. This gives diurnal animals greater visual acuity. Humans are diurnal animals
Nocturnal Animals
Nocturnal animals, like cats, have reflective eye cells that bounces light back to the photoreceptors giving the animal a second chance at catching the thing in its sight. Nocturnal animals have lower visual acuity than diurnal animals
Rods, Cones, and the Optic Nerve
Rods and cones produce neural signals in response to light. The rods and cones transmit information about light and color to the brain via the optic nerve
Cones
Are used in daylight vision and cluster in the center of the gaze
Rods
Are much more sensitive, are used for night vision. Rods can be found in the periphery of the eye. Rods do not detect color. They only use light to perceive value (light and dark).
Cones = Color
Rods = Value
There are 3 kinds of cones but only one kind of rod. The three different kinds of cones (red, green and blue cones) allow us to detect different wavelengths of light-this is how we see color.
Primary Colors
The primary colors when
we talk about pigment are
red, blue and yellow. The
primary colors in vision are
red, green and blue and are
connected to the short,
medium and long
wavelengths of light
detected by the three
types of cones in our eyes.
Why would the primary
colors in vision correspond
to the RGB color mode?
Visible Light
Visible is the range of light
that our cones can
respond to. Is visible light
the same for all animals?
Mantis Shrimp
Mantis shrimp are able too
see 12–16 colors depending
on the species. By
comparison, humans are
only able to see three: red,
green and blue
Color Blindness
Color blindness is caused
by a mutation in the red or
green cone. It’s carried on
on the X chromosome.
Because men only have
one X chromosome
(women have two), they
have a higher frequency of
color blindness. 10% of
men are color blind while
less than 1% of women are
color blind.
Color blindness doesn’t
mean that you see the
world in black and white. It
just means that you see
certain color pairs as
identical.
Luminance
Luminance (value) is
perceived lightness. Luminance does not have
a numerical value. Our
perception of luminance is
based on our sensitivity to
light.
Our ability to gauge
luminance (tell the
difference between light
and dark) is key to depth
perception, three
dimensionality and
movement. Color does not
factor into the perception
of these things.
Blue light appears dim and
yellow light appears bright
—even if they have the
same number of photons.
The sense of luminance is
created by the
wavelengths of the light.
Bruce Nauman’s natural
light, blue light room.
Nauman’s use of neon as a
medium recurs in his works
over the decades. He uses
neon to make allusions to
the numinous connotations
of light
Our eyes analyze color and luminance separately
Impression Sunrise
Monet’s Impression Sunrise The sun has the same luminosity as the sky. It makes the sun look weird and eerie. In nature the sun is lighter than the sky.
