NATS 1870 Study Guide - Quiz Guide: Visual Phototransduction, Ewald Hering, Filter Paper
19 Jun 2018
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Understanding Colour- Exam Notes
What is color?
Science meets arts
Multidisciplinary – physics, astronomy, chemistry neuroscience evolutional biology
Light + perception
Huma vision system differentiating between wavelengths of light
The reason why things have different colours is because every atom and molecule has
different set of quantized levels; this means that every different type of molecule or atom
will produce a different characteristic set of colours or what we refer to as a spectrum
Colour can be measured as either the frequency OR wavelength of light
Black and white ae not colours; black is the absence of light (absorbed) and white is the
reflection of light (superposed)
Properties of colours-
oHue- this is the colour we actually see; related to wavelengths of light hitting our
eyes; dominant wavelength; we can use linear spectra to show this type of colour
Non-spectral colours are when more than one colours wavelength is
bright, so our eyes add the colour to produce what we see. For example,
purple which is at the far end of the spectrum (400nm), so we usually see
it as a combination of different wavelengths. Here we use chromaticity
diagram
oSaturation- or chroma is the variation from a pure colour or the intensity; the
more saturated a colour the narrower the spectral peak; fluoresce will have very
high saturation; we can lower the saturation of a reflective surface or pigment by
adding white or gray or black to the pure colour
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Tones are pure colours mixed with a complement until you reach a gray
colour
Tints are pure colours mixed with white until pure white is obtained
Shades are pure colours mixed with black until a pure black is obtained.
Tone tints and shades are only applied to pigment application
oValue- tone or brightness are all similar or related properties; measure of the
amount of light, irrelevant of colour that is reflected from a surface; measured in
comparison to a standard black or white surface
Additive and subtractive systems-
oAdditive is the one in which wavelengths of light are added together; the more
colour you add, the brighter something will seem; adding correct colour
combination to reach white; eye mixes colour internally; individual colours sent
to eye; additive mixing happens with lights
oSubtractive is when pigments which reflect light are used. The more different
pigments the more light is absorbed so that something becomes darker; eye sees
colour externally on the surface; composite colour sent to eye; subtractive mixing
happens with print
Painter’s primary- red, yellow, blue and sometimes green along with
black and white
Subtractive primaries- Cyan, Magenta,
and Yellow (for printing we use CMY
and K (black)
Additive primaries- red, Blue, and
Green (these are not the mixtures for
pigments)- ITTEN’S COLOUR WHEEL
oA colour wheel is the combination of the primaries as they are mixed in varying
amounts
oPrimary colours- red, blue, and yellow; mix them together to populate the colour
wheel
Red + blue= purple so the complement will be yellow
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find more resources at oneclass.com
Secondary colours- purple green and orange in subtractive system;
complements of the primary colour
Tertiary colours- the mixtures of primary and secondary colour that are
next to each other in the colour wheel
Photoreceptors
There are three types of colours receptors in the human eyes
They are sensitive to red blue and green
Thus, all the colours we perceive are produced
by mixing these three colours (primaries)
Colour schemes- rectangle, square, split
complementary, complementary, triadic,
and Analogous
What is light?
Form of energy with both electric and
magnetic components; a transverse
electromagnetic wave (TEM)
Energy- is the amount of work and is measured in Joule (J); energy depends on mass, distance,
speed
oEnergy is never destroyed, it can only be converted to another form- conservation
law of energy
oThree types of equation- Kinetic (motion), potential (energy due to object’s position),
and radiant (energy due to object’s wave/particle properties)
Can behave as a particle or as a wave
Wave: an oscillation or back and forth movement through a medium
oTwo types- longitudinal (parallel to motion) and transverse (perpendicular to motion)
oWaves are transporters of energy
(longer wavelengths have lower
energy and shorter wavelengths
have higher energy)
Wavelength (λ)- symbol is called
lambda- distance between successive
crests or troughs of the wave; the distance
is measured in m, cm, nm
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Multidisciplinary physics, astronomy, chemistry neuroscience evolutional biology. Huma vision system differentiating between wavelengths of light. Colour can be measured as either the frequency or wavelength of light. Black and white ae not colours; black is the absence of light (absorbed) and white is the reflection of light (superposed) Properties of colours: hue- this is the colour we actually see; related to wavelengths of light hitting our eyes; dominant wavelength; we can use linear spectra to show this type of colour. Non-spectral colours are when more than one colours wavelength is bright, so our eyes add the colour to produce what we see. For example, purple which is at the far end of the spectrum (400nm), so we usually see it as a combination of different wavelengths. Tones are pure colours mixed with a complement until you reach a gray colour. Tints are pure colours mixed with white until pure white is obtained.
