~Chapter 9 - Lecture Section 9.1 Flashcards
True or False: Homo Sapiens type of colour-vision is fairly rare among mammals
True. The colour-vision that we enjoy is actually fairly rare among mammals.
What are the proposed theories about why primates developed colour-vision?
It has been proposed that primates developed colour-vision due to their arboreal ecology. Another proposal is that good colour-vision can compensate for the poor sense of smell that primates have.
What type of colour-vision do most mammals have?
Other mammals are typically Dichromatic
What animals sometimes have more than 3 Cones?
Birds and lizards have sometimes more than 3 cones
There is an ___ to having colour information. It creates a very vivid use of colour during visual perception.
evolutionary advantage
Why is it an evolutionary advantage to have colour information?
A Rod Monochromat, meaning they have no colour signals at all, would have a lot of trouble foraging for ripe berries and fruit.
Colour is important for our ___ when we consider studies that look at the accuracy and speed of ___ objects if they were appropriately or inappropriately coloured.
object processing // naming
Who initially described light?
Newton initially described light with his prismic experiments, where he proposed that white light is made up of different “particles” (wavelengths). This was later revised to light being composed of different wavelengths, or acting as these photons.
How did Newton prove his theory on colour?
When passing white light through a small aperture, such that it entered a prism, Newton showed that the white light could be separated into these constituent wavelengths, and when he isolated these wavelengths individually, he noted that it couldn’t be divided anymore.
And so he proposed that white light was composed of all these different wavelengths, and that these long wavelengths show less refraction, that is to say, less bending when they go through a prism, than the short wavelengths.
Long Wavelengths show ___ refraction, that is to say, ___ bending when they go through a prism
less // less
What is Reflectance?
Reflectance is the amount of incident light that is reflected off the object
The percentage of light reflected from a surface.
When there is Incident Light, light shining from some light source, there will be ___ off of an object.
Reflectance
Coloured objects exhibit ___ due to the molecular structure of the material that they’re made out of.
selective Reflectance
Coloured objects exhibit ___ due to the molecular structure of the material that they’re made out of.
Selective Reflectance
A white piece of paper reflects all wavelengths ___, so we have white incident light, and all wavelengths are reflected more or less equally to our eye so this paper will appear light.
equally
A red piece of paper, from white incident light, absorbs the ___ wavelengths of light and selectively reflects ___ wavelengths of light, the absorbed wavelengths of light are turned into heat
shorter // long
What is Selective Transmission?
Allow only select Wavelengths to pass through
When some wavelengths pass through visually transparent objects or substances and others do not. Selective transmission is associated with the perception of chromatic color.
Where does Selective Transmission occur?
See-through items such as glass or liquids
What is Selective Reflection?
When an object reflects some wavelengths of the spectrum more than others.
How would light react to a red glass of cranberry juice
There is Selective Transmission, only the red wavelengths can pass through it, where the other wavelengths are absorbed. Instead of Selectively Reflecting long wavelengths to appear red as a solid object would, these transparent liquids and glass will allow certain wavelengths to pass through while absorbing other wavelengths.
Reflectance Curves are useful when talking about the visual stimuli and the responses of ___.
photoreceptors
How is Reflectance Curve measured?
A plot showing the percentage of light reflected from an object versus wavelength.
In a Reflectance Curve, coloured objects will have a ___ in the reflectance curve.
peak
What is the reflectance of green Lettuce?
For green lettuce, there is some reflectance at these low and higher wavelengths, but it peaks at the middle, and so that is why we see it as green.
What is the reflectance of a Tomato?
For a tomato, the peak is over in the long wavelengths, and so we see it as red.
Items that have ___ are seen as black, grey, or white.
Flat Reflectance Curves
___ paper absorbs most incident light, and so it has very ___ reflectance.
Black // little
___ paper reflects most of the incident light, and so it has ___ reflectance across all wavelengths and it is very high.
White // equal
What is the reflectance of Grey?
Grey, depending on how dark the gray is, is going to be in the middle.
What do you get when you mix yellow and blue paints?
Blue + Yellow = Green paint
What are the qualities of Blue paint?
- Selectively absorbs long wavelengths.
- It has a little bit of reflectance of medium wavelengths
- Strong reflectance of short wavelengths
What are the qualities of Yellow paint?
- Strong absorption of Short wavelengths
- Intermediate reflectance of Medium wavelengths
- Strong reflectance of Long wavelengths
What happens when you mix paints together?
When you mix the paints together, you’re mixing the pigments, and the main job of pigments is to absorb the different wavelengths. So the mixture is acquiring the properties of one another.
What is the main job of pigments?
The main job of pigments is to absorb the different wavelengths.
What happens when you mix yellow and blue paints?
This mixture is acquiring the properties of absorbing very strongly the long wavelengths from the blue, and it’s also taking on the properties of absorbing the short wavelengths from the yellow. This mixture of paints, now strongly absorbs the long and short wavelengths, but it will still allow, as these other pigments do, the medium wavelengths to be reflected away.
What is Subtractive Colour Mixing?
Subtracting wavelengths from the mixture, and the only thing that is allowed to reflect out is the wavelength that the two pigments have in common.
Mixing paints is an example of ___.
Subtractive Colour Mixing
When we look at the Selective Reflectance curves of Blue and Yellow, we see there is a common area in ___, that will be reflected by all of this absorption by the yellow and blue in the mixture it ends up subtracting away and leaving only this common reflectance.
green //
What is Additive Color Mixing?
Additive Color Mixing is what happens when you mix light
The creation of colours occurs when lights of different colours are superimposed (placed or laid over something else, typically so that both things are still evident.)
Blue + Yellow = ___ Light
Red + Green + Blue = ___ Light
Red + Green = ___ Light
Green + Blue = ___ Light
Red + Blue = ___ Light
White // White // Yellow // Cyan // Magenta
Why are there pixels in tv and phone screens that have red, green and blue components?
By mixing these three complementary lights in different proportions you can get any colour in the spectrum, this is an example of Additive Color Mixing
InkJet cartridges for printers do ___ using Cyan, Magenta, Yellow, and Black
Subtractive Colour Mixing
What type of colour mixing is most common in our daily lives?
Both kinds of colour mixing are extremely common in our daily lives, we are exposed to the products of Additive and Subtractive Colour Mixing everyday.
How do all monitors (computers, phones, etc) create colours on our screen with pixels?
All monitors have tiny little pixels and subpixels within them that are Red, Green, and Blue bars and they turn on or off depending on what colour they need to make
By mixing ___, ___, and ___ lights in different proportions you can get any colour in the spectrum.
Blue // Green // Red
What is Intensity (Value or Brightness)?
Shades of gray = Achromatic colours, going from Black through Gray, and all the way to White.
The way you’d change from Black through Gray to White is by changing the ___.
Intensity/Value/Brightness
In a Selective Reflectance Curve, we’d have a flat line that would be very low, but homogeneously flat for ___, and each line representing each colour getting ___ would get higher and higher.
Black // lighter
What is Wavelength?
Chromatic colours or Spectral colours or Hue.
How are Chromatic/Spectral/Hue Colours produced?
This is produced with single wavelengths by going from short wavelengths (400nm) all the way through to long wavelengths (700nm).
What are Non-spectral colours?
Non-spectral colours are not on the spectrum because they are a mixture of colours (e.g. brown)
How many steps in the spectrum (Wavelength/Hue/Chromatic Color/Spectral Color) can we see?
We can discriminate at least 200 steps in the spectrum
How many steps of Brightness/Value/Intensity can we see?
We can discriminate at least 500 steps of brightness/Value/Intensity.
How many steps of Saturation can we see?
We can discriminate at least 20 steps of saturation.
What is Saturation?
Saturation is going from homogeneously white, and gradually adding a single wavelength to it until it becomes fully saturated for that pure colour.
Example: Adding a long wavelength to white will create this gradient going from whites through pinks all the way to red
Where does the term Saturation come from?
This terminology comes from textile dyes, where you start off with white wool, and as you saturate it with dye it becomes coloured
How many colours can we see overall?
200 steps in Hue x 500 steps in value x 20 steps in saturation = We have at least 2 million colours that we can see, potentially more.
(≥200) ×(≥ 500) ×(≥ 20) ≈ at least 2,000,000
How can we summarize Hue, Value, and Saturation into one entity?
By organizing them into a colour solid
What are Colour Solids?
Colour Solids are 3-dimensional colour spaces where the coordinates within the space define the colour. It is based on perceived colours.
What are Colour Solids?
Colour Solids are 3-dimensional colour spaces where the coordinates within the space define the colour. It is based on perceived colours.
What are colour solids often used for?
For picking colours on a computer user interface
Moving your cursor on the rotational axis of a Colour Solid indicates the ___.
Wavelength/Hue/Chromatic/Spectral Colour
Moving your cursor on the vertical axis of a Colour Solid indicates the ___.
Value/Brightness/Intensity
Moving your cursor on the radial extent of a Colour Solid indicates ___. Toward the middle, it becomes white and desaturated. Toward the edge it becomes very coloured, saturated.
Saturation
Do Colour Solids include Non-Spectral Colours?
No, because it’s picking individual colours it does not include non-spectral colour.
On a Colour Solid, when you are mixing blue and yellow light, if you mix them in equal proportions you will get ___, and you can add blue in various proportions to cancel out the yellow and bring it closer to white
white
On a Colour Solid, if you have 75% yellow and only 25% blue, bringing the cursor closer to the edge is ___ and it’s approaching a 50/50 mixture where it will become ___.
desaturating // white
Do Wavelengths have colour?
Wavelengths themselves don’t have any colour to them, they are just electromagnetic radiation that oscillates at different frequencies. There is nothing in the photons that makes them red or blue or green
We have ___ that can distinguish wavelengths of light
Sensors (S, M & L Cones)
What is Colour?
Colour is the brain’s way of informing us what wavelengths are present, its a construction that is produced in our minds
___ make use of the physical differences between wavelengths
Short, Medium and Long Wavelength Cones
When asking the question “Do others perceive the colour of a red apple the same way I do?”, what two questions does this produce about colour perception?
Q: How does the mind create the experience of colour?
A: This is the Mind/Body Problem stated for colour, there’s no real answer for it
Q: How does the nervous system determine which wavelengths are present?
A: This is answerable, there are two theories
Selective Transmission is associated with the perception of ___.
chromatic color
What colour is an example of a Non-spectral colour?
Brown
What colours do InkJet cartridges mix?
Cyan, Magenta, Yellow, and Black
What Colour-vision do humans have?
Trichromatic color vision
