Topic 7- Perceiving Colour Flashcards
What are 3 functions of colour perception?
- Can help us identify things
- Can help us classify things
- Can help inform our actions
What is object colour?
Determined by the specific wavelength of light that are reflected from, or transmitted through, that object.
What are chromatic colours?
3pts
- Colours with hue
- Ex- red, blue, green
- Occurs when some wavelengths are reflected from an object more so than others (selective reflection)
What are achromatic colours?
3pts
- Colors without hue
- Ex- white, black, and all shades of grey
- Occurs when light is reflected from an object equally across the spectrum
What is selective transmission?
Occurs when only some wavelengths pass through transparent objects, while other wavelengths do not
What are the corresponding perceived for wavelengths reflected or transmitted?
- short
- medium
- long and medium
- long
- short, medium, long
Short –> blue
medium –> green
long and medium –> yellow
long–> red
long medium, and short–> white
- Mixing paints
- Mixing light
which is adding wavelengths vs subtracting wavelengths
- Mixing paints: subtracting wavelengths
- Mixing light: adding wavelengths
What happens when mixing paint ex- blue + yellow paint ?
Combined…
Combined, both paints absorb the same wavelengths they absorbed when they were alone, so only the wavelengths reflected are those reflected by both
Colours that appear in the visible spectrum
What are these?
Spectral colours
- Colours that do not appear in the visible spectrum
- Are mixtures of spectral colours
What are these?
Nonspectral colours
Perception of chromatic colours, or shades/variations of these colours.
What is this?
Hue
What is saturation?
3pts
- Amount of “whiteness” added
- More “white” = low saturation
- Desaturated means faded/washed out
What is the value (lightness)?
2pts
- The “light-dark” dimension
- Decreases as colours becomes perceptually darker
What determines our perception of color in terms of the physiology of color vision? What is trichromacy of color vision?
2pts
-Our perception of colour is determined by the activity of 3 different cone photopigments that have different sensitivities (short wavelengths/blue, medium wavelengths/green/long wavelengths/red)
- If you have all three, you can perceive color
What is monochromacy?
2pts
- Complete colour blindless/ “rod-only vision”
- Absence of cone receptors results in the perception of only achromatic colors (white, black and grey)
What is dichromacy?
2pts
- Colour vision but only with two pigments present
- Can see some chromatic colours but its hard to distinguish between some colours
“Red-green colour blindness”
1% of males, 0.02% of females
- No long-wavelength photopigment
What type of dichromacy is this?
a. protanopia
b. Deuteranopia
c. Tritanopia
Protanopia
“Red-green colour blindness”
1% of males, 0.01% of females
- No medium-wavelength photopigment
What type of dichromacy is this?
a. protanopia
b. Deuteranopia
c. Tritanopia
Deuteranopia
“Blue-yellow colour blindness”
0.002% of males, 0.001% of females
- No short-wavelength photopigment
What type of dichromacy is this?
a. protanopia
b. Deuteranopia
c. Tritanopia
Tritanopia
Our perception of colour is determined by the activity of two opponent mechanisms:
Complete the sentence
How many colors did Hering believe in?
- a blue-yellow mechanism and a red-green mechanism
- Hering proposed that there are four main colors: red, green, yellow, and blue. All other colors are seen as combinations of these four.
What is color constancy?
Our perception of an objects color remains relatively constant when the amount of illumination is changed
What is lightness constancy?
Why does it occur?
Our perception of an objects lightness (white vs black) remains relatively constant under different intensities of illumination
Occurs because the relative proportion of light being reflected into the eye stays the same regardless of illumination
