Color Harmony and the Opponent-Process Channel Theory
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Transcript of Color Harmony and the Opponent-Process Channel Theory
Color Harmony and the Opponent-Process Channel Theory
Christina LewisPsych 159
TRICHROMATIC THEORY Thomas Young and Hermann von Helmholtz, 18’th-19’th
century
Opponent-Process Theory
• 1878 Ewald Hering
• Certain color combinations don’t exist (we never see them), such as reddish-green or yellowish-blue
• Three receptor types, each with opposing pairs: red green, blue yellow, black white
Opponent Neurons
• Excitatory response to some wavelengths and inhibitory response to others
• Red-Green receptors cannot send information about both colors at the same time
• Responses to one color of an opponent channel are antagonistic to those to the other color.
**More efficient, given that for the cones, responses to certain wavelengths overlap. Differences are more important.
CONES BIPOLAR CELLS GANGLION CELLS
PARVOCELLULAR MAGNOCELLULAR
Processes differences between L & MCones, Red – Green differences
Processes difference between S cones, blue-yellow differences
Intensity of light
How it Works• Red-Green Channel: The difference
between long-wavelength and middle-wavelength cone signals.
• Yellow-Blue Channel: The difference between short wavelength cones and the sum of the other two cones.
• *Luminance Channel*: Based on inputs from all the colors. Detects the difference in brightness of color information.
ISOLUMINANCE DIFFERENT COLORS - SAME BRIGHTNESS
Youhellohavepsychnoclassproblemthisreadingisonlyathereadinggreentestwords.
This is a very bad words-on-background color-pair, because there is very little difference between the luminance of the color dark-blue and the luminance of the color black.
BAD BAD BAD DON’T DO THIS IN YOUR FUTURE POWERPOINTS
Implications•Color-opponent channels:•Color is good for SEPARATING OBJECTS• Separating regions
• Luminance Channel:•Contrast transmits SHAPE INFORMATION
(**edges**)• Fine detail
Other Important Properties of Opponent Channels
• Luminance > Purely Chromatic Information:• (for many aspects of vision including):• Stereoscopic depth: Cannot detect differences in depth based purely on color channel information
Other Important Properties of Color Channels• Motion Perception: • Luminance > Purely Chromatic Information• If gratings of different colors but equal luminance are moving, we detect the
speed much slower (or for some humans, completely immobile) as compared to a grating of very large contrast difference (for example a black and white or black and yellow grating).
After-Images-Fatigue of one color receptive causes stimulation of its opponent color in the pair