Perceiving Color Chap 9 Flashcards
Sensation and Perception, 8th edition by E. Bruce Goldstein
The colors of light in the spectrum are related to wavelength, but what about the colors of objects?
The colors of objects are largely determined by the wavelength of light that are REFLECTED from the objects into our eyes.
what does the reflectance curve plot?
plots the percentage of light reflected versus wavelength (x-wavelength and y-percentage)
The color black…
absorbs all the colors of the spectrum.
The color white…
reflects all the colors of the spectrum.
Short wavelength…
medium wavelengths..
Long wavelengths…
we perceive blue.
we perceive green.
we perceive red.
what is a chromatic color?
When some wavelengths are reflected more than others or a color that has a hue. Ex: colored paints
what is an achromatic color?
When light reflected is similar across the full spectrum- that is contains no hue- as in WHITE, BLACK and GRAYS.
How do transparent things like liquids get their color?
They go under selective transmission- when some wavelengths pass through visually transparent objects or substances and others do not.
What is additive color mixture?
Def: The creation of colors that occurs when lights of different colors are superimposed.
When colored lights are superimposed is that all the of the light that is reflected from the surface by each light when alone is also reflected when the lights are superimposed.
What happens when you mix blue and yellow lights?
When 2 spots are projected into a white surface, all of the wavelengths that hit the surface are reflected into the observer’s eye.
The blue spot consists of a band of short wavelengths (when projected alone) the short wavelength is projected into the observers eye.
The yellow spot consists of medium and long wavelengths (alone) which are reflected into the observers eye.
what is subtractive color mixing?
Def: the creation of colors when paints are mixed together.
When paints are mixed, both paints still absorb the same wavelength they absorbed when alone, so the only wavelength reflected are those that are reflected by both paints in common.
What happens when you mix blue and yellow paint?
The blue blob of paint ABSORBS long-wavelength (L=red) light and REFLECTS some short and medium wavelength (S=blue and M=green).
The yellow blob absorbs short wavelength light (S=blue) and reflects medium and long wavelengths lights (M=green and L=red).
Because MEDIUM wavelenths are the only ones reflected by both paints in common, amixture of blue and yellow paints appears GREEN.
What are the key findings for the color matching experiments?
- By correctly adjusting the proportions of 2 wavelengths in the comparison field, it was possible to match any wavelength in the field.
- People with normal color vision cannot match all the colors of the spectrum only using 2 wavelengths. BUT people who are color difficient can match the colors of all wavelengths by using the 2.
What is a metamer?
Def: Two lights that have different wavelength distributions but are perceptually identical.
Metamerism-Situation in which two physically different stimuli are perceptually identical
In vision, this refers to two lights with different wavelengths distributions that are perceived as having the same color.
What are Ishihara plates?
These are for testing colot deficiency. People with normal color vision see a “74” but people with a form of red-green color deficiency might not see the “74”.
