Color Vision txtbk Flashcards
Color vision:
The ability to see differences between lights of different wavelengths
Qualities that describe how we perceive color:
Hue, Saturation, Brightness
Two physiological mechanisms that create our experience of color:
Trichromacy and Opponency
Color constancy and Light constancy
Our ability to see things as having the same color and lightness under different conditions
Color vision deficiencies/ “colour blindness”:
condition in which people experience partial or total loss of their ability to see color
What did Isaac Newton postulate?
Our perception of color comes from the interaction between receptors in the eyes and the wavelengths of light reflected from the surface of objects - a specific experienced color is evoked by specific wavelengths present in the light
The visible spectrum ranges from :
400 to 700 nm
Visible spectrum:
The portion of the electromagnetic spectrum in the range of about 400 to 700 nm; people with normal color vision perceive differences in wavelengths as differences in color
Is color in material things
color is NOT in light or material things: color is a perceptual experience evoked by specific wavelengths of light reaching our eyes
Spectral power distribution:
The intensity (power) of a light at each wavelength
heterochromatic light:
Light that consists of more than one wavelength
monochromatic light:
Light that consists of only one wavelength
The SPD of a monochromatic light:
Is a vertical spike
sunlight, incandescent bulbs and fluorescent bulbs all emit what is called :
White light
White light is heterochromatic light that:
(1) contains wavelengths from across the entire visible spectrum
(2) has no really dominant wavelength
The SPD of an idealized white light would be:
A horizontal line: A light in which all wavelengths across the visible spectrum have exactly equal power
The SPD of __ is quite close to an idealized white light
sunlight
SPD of light from incandescent bulb is
more intense toward the yellow and red end of the spectrum
SPD of light from a fluorescent bulb:
has spikes at the “short” and “medium” wavelengths that make fluorescent light somewhat more bluish than sunlight
Achromatic light is synonymous with:
white light
Achromatic light:
heterochromatic light containing wavelengths from across the visible spectrum, with NO really DOMINANT wavelengths: perceived as more or less colorless
A graph of the spectral reflectance of a surface shows:
The percentage of light at each wavelength that the surface reflects rather than absorbs
Black, gray and white paper have similarly flat reflectance curves, which means:
They reflect the same percentage of all wavelengths - but white paper reflects overall much more light than black paper
The perceived colour of things depends on:
(1) The SPD of the light source
(2) How things reflect light