Chapter 9 - Lecture Section 9.3

Question 1

Humans Retinas have ___ proportions of L-Cones and M-Cones

Answer 1

variable

Question 2

True or False: Depending on what the Wavelength that’s being reflected is, is the colour that we’ll see

Answer 2

False. It’s more complicated than this for a number of reasons.

Question 3

The Sensors/Cones can be different from person to person, but despite this individual variability, people are still generally ___ in the way they recognize colours.

Answer 3

consistent

Question 4

___ Wavelength Cones are always evenly distributed, but sparse in the ___ Periphery, this is fairly common across all people.

Answer 4

S // Near

Question 5

What is Colour Constancy?

Answer 5

Perception of colour remains relatively unchanged despite changes in ambient illumination

Question 6

What is an example of Colour Constancy?

Answer 6

Think of all the changes in ambient illumination you would experience on a normal day, you’re inside your house looking at your shirt which is green, then you go into the living room where the illumination condition is different, and the sweater doesn’t look like it’s changed colour.

Question 7

A Green sweater has a peak of reflectance of 495nm under LED light, but 570nm under incandescent light, yet it always looks like ___ green colour, this is referred to as ___.

Answer 7

the same // Color Constancy

Question 8

Sunlight is more or less ___ light.

Answer 8

white

Question 9

Incandescent light, which is the old-style light bulb that has a tungsten filament, has very ___ looking light, where there are much more ___ wavelengths and relatively few ___ wavelengths.

Answer 9

yellow-ish // longer // short

Question 10

In a modern LED light bulb, the ___ light that is produced is because of several different coloured LED ___.

Answer 10

white // photodiodes

Question 11

What are the mechanisms that have been shown to contribute to Colour Constancy perception?

Answer 11

Chromatic Adaptation
Effect of the Surroundings
Memory and Color

Question 12

What is Chromatic Adaptation?

Answer 12

Chromatic Adaptation refers to the selective bleaching of certain photoreceptors depending on the ambient lighting.

Question 13

What is Ambient lighting?

Answer 13

Ambient lighting would be the lightbulb in the room that is casting its light onto all the surfaces, and those surfaces are then reflecting light into your eye, but the wavelength that is being reflected is dominated by the light source.

So if it’s a Red light, most of the light that’s reflected is going to be a Longer wavelength.

Question 14

When our eyes adapt to ambient light, it becomes ___ to the wavelengths.

Answer 14

less sensitive

Question 15

When the room that the subject is sitting in and also the other room is illuminated by White light, and the colour sample is Green, the subject will say the Green paper is ___.

Answer 15

Green

Question 16

When the sample room has Red illumination, but the ambient lighting where the person is sitting has White illumination, an illusion is produced, and the subject reports that the paper has shifted towards ___, and will look ___.

Answer 16

Red // kind of yellowish or brownish

Question 17

Why does the subject perceive that the paper looks kind of yellowish or brownish when the sample room has Red illumination and the ambient lighting where the person is sitting has White illumination?

Answer 17

This is because the observer is not adapted because of the ambient light in their room being White, so they are adapted across all wavelengths more or less equally

Question 18

Both the sample room is illuminated in Red light, and the subjects room is illuminated in Red light, so the subject becomes adapted to Red, all of the Red light that is reflecting off of these surfaces are flooding the eye with predominantly L wavelengths, and so the L wavelength cones are becoming adapted, they are losing sensitivity to this l wavelength light. The result is that the colour perception of Green paper is now slightly shifted toward ___ rather than strongly shifted.

Answer 18

Red

Question 19

___ decreases sensitivity

Answer 19

Selective bleaching

Question 20

With Chromatic Adaptation, as you are becoming adapted, less sensitive to the dominant colour, it appears to fade and other colours are ___ to pick out.

Answer 20

easier

Question 21

With Chromatic Adaption, what happens when there is lush illumination/a lot of green surfaces?

Answer 21

We become less sensitive to Green and this allows other colours to stand out, like flowers or berries.

Question 22

With Chromatic Adaption, what happens in an Arid environment/a lot of Yellow surfaces?

Answer 22

Like in a fall environment, where all the grass has turned Yellow, you become less sensitive to Yellow

Question 23

Chromatic Adaptation can cause adaptation to the ___ colour in the ___ lighting.

Answer 23

dominant // ambient

Question 24

Chromatic Adaptation helps with ___ and searching for ___ in the scene.

Answer 24

object detection // novelty

Question 25

What is the evolutionary advantage to Chromatic Adaptation?

Answer 25

Dominant colours appear to fade and other colours are more easy to pick out.

If you are foraging for flowers or berries, their colours will become more apparent.

This helps with object detection and searching for novelty in the scene.

Question 26

Our percept of colour is strongly dependent on the ___.

Answer 26

surrounding colours

Question 27

One effect that contributes to Colour Constancy is the effect of the ___.

Answer 27

surrounding

Question 28

___ colours can affect how you may perceive a colour.

Answer 28

Neighbouring

Question 29

Which of the mechanisms that contribute to Colour Constancy perception has the smallest and most subtle effect?

Answer 29

Memory and Color

Question 30

___ available about the colour of objects that we encounter in our daily lives will produce a small influence on the perceived colour.

Answer 30

Top-down Information

Question 31

In a study where subjects look at fruit where the saturation was low, in the cases where the fruit was basically achromatic, subjects would still report that the lemon was slightly tinted yellow or an apple was slightly tinted red, why is this?

Answer 31

The effect of Memory for Colour was superimposing a colour onto this fruit just by recognizing its identity.

Question 32

What was the underlying issue that caused “The Dress” controversy online?

Answer 32

Most of the blue/black vs. white/gold perceptions boil down to mechanisms of Colour Constancy and assumptions about (Ambient) lighting

Question 33

If you assume that the Ambient lighting is very White, “The Dress” will appear to have a ___ hue

Answer 33

Gold and White

Question 34

If you assume that the Ambient lighting is Yellow, then “The Dress” will appear ___.

Answer 34

Blue and Black

Question 35

What is the true colour of the infamous Dress?

Answer 35

Black and Blue

Question 36

The Ambient lighting of the room that caused the infamous Dress controversy online was ___.

Answer 36

Yellow

Question 37

What are the factors that contribute to how one perceives the colour of the infamous Dress?

Answer 37

• The surroundings of the monitor and the surroundings in the room around you when you looked at the dress can lead to assumptions about the ambient lighting and can produce this illusion.
• Assumption about the (Ambient) lighting

Question 38

Why do colour perception mistakes like the infamous Dress incident happen only in photographs and not real life?

Answer 38

\When you’re seeing something live in person, you have information about the Ambient lighting, you have Chromatic Adaptation occurring, Memory for Colour, and you are able to use many more of these Colour Constancy mechanisms.

Question 39

What is Lightness Constancy?

Answer 39

txtbook: The constancy of our perception of an object’s lightness under different intensities of illumination.

For even illumination, we see the true Achromatic properties of an object irrespective of the illumination. Similar to Colour Constancy, but it is talking about the brightness or darkness of different parts of an object.

Question 40

The perceived brightness of an object depends on our perception of ___, making use of the ___.

Answer 40

illumination conditions // Ratio Principle

Question 41

We have a b&w checkerboard being viewed under dim illumination, indoor lighting, at 100 units. So the white is reflecting 90% of the photons, and the black is reflecting 9% of the photons.

We bring the same checkerboard into the noon sun where it is much brighter, now we have 10,000 units of illumination.

The surface hasn’t changed, this is still gonna reflect 90% off white and 9% of black.

Why is this?

Answer 41

Even though the black square is reflecting 100x more light in the light condition than in the dim condition, nobody is going to say that the black square has turned white all of a sudden, what we take into account is the ratio of reflectances off of a surface.

Question 42

We have two surfaces, a dark and a light surface, and we have two illumination conditions, either where there is 1000 units of light or 100 units of light.

Which is the most important ratio?

Answer 42

The most important ratio is the ratio between the amount reflected off the dark surface and the light surface. -The ratio of the dark surface to the light surface is 1:9

Question 43

Why do the dark and light rectangles have the same relative reflectance to each other in the dark as it does in the light?

Answer 43

Because the ratio has not changed

Question 44

The black curtain with a white spotlight that is often seen during plays and concerts is an example of ___.

Answer 44

Lightness Constant

Question 45

lluminate a black disk against a black background and it appears ___, but introduce white paper and the disc appears ___, and you can see the ratio of those different surfaces, this is due to the ___.

Answer 45

white // black // Lightness Constant

Question 46

Illumination is rarely ___.

Answer 46

even

Question 47

Most of the time, objects that you’re encountering in your daily life have shadows on them, either your own shadow, or the shadows of other objects, and this introduces further complexity when trying to discern the ___ of the different ___ within an object.

Answer 47

brightness // components

Question 48

What is a Reflectance Edge?

Answer 48

Where there is a true difference between the dark parts of an object and the light parts of an object, so this is having to do with the surface properties of the object.

An edge between two areas where the reflectance of two surfaces changes.

Question 49

What is an Illumination Edge?

Answer 49

Where a shadow is cast onto the object, and it is creating a difference in the amount of light that is hitting the surface, and so this is referred to as an Illumination Edge.

The border between two areas created by different light intensities in the two areas.

Question 50

What is the problem with Reflectance and Illumination Edges?

Answer 50

Sometimes telling the difference between Reflectance and Illumination Edges can be challenging.

For example, when we talked about object processing and the way we would group or segregate different components with an image, we noted that early artificial vision had a hard time segmenting an image if it had uneven illumination.

Question 51

Is the difference between two paint colours next to one another on a wall a Reflectance Edge or an Illumination edge?

Answer 51

This difference is a result of the properties of the pigment in the blue and pink paint. The difference has to do with the paint that is put onto the surface, so this is a Reflectance edge.

Question 52

Is the shadow that is cast across half a wall of paint of a single colour, making one side appear to be darker a Reflectance Edge or an Illumination edge?

Answer 52

Illumination Edge, the difference between dark and light isn’t due to the properties of the paint, it is due to the uneven illumination because of the shadow that is cast

Question 53

How can we know something is a shadow?

Answer 53

There are a number of clues, usually, a shadow is at the bottom of an object.

The shadow’s penumbra (fuzzy border) helps distinguish a shadow from an object.

Question 54

What is a Penumbra?

Answer 54

The fuzzy border on the edge of a shadow

Question 55

There is an interaction between ___ perception and light perception

Answer 55

object

Question 56

Where does the interaction between object perception and light perception come from?

Answer 56

This comes from the understanding of the physical regularities of shadows, how shadows are normally cast, how light normally acts, that contributes to our perception of light and dark and distinguishing illumination from reflectance edges.

Question 57

What can effect the interaction between object perception and light perception?

Answer 57

Sometimes, there are pictures that can play with these heuristics that our visual system uses

Question 58

We see an image that makes us think that a green cylinder is creating a shadow, but it turns out the shadow is actually just the result of paint made to look like a shadow, what happened?

Answer 58

Our brains are performing a different Lightness Constancy for the different regions, making us perceive two areas on the image are different colours when they are the same.

Question 59

Sometimes, if the ___ is removed, we are not able to apply Top-Down ___ about how objects normally interact with light.

Answer 59

Spatial Context // physical regularity

Question 60

You take a piece of paper and fold it in half, and have light coming from the sides such that one half of the paper is in shadow and the other is light, you can see it’s an angled surface where one side is in shadow and one is in light.

You take the same piece of paper and view it through a peephole, and suddenly the piece of paper looks like it is painted dark on one side and light on the other.

What is happening here?

Answer 60

By viewing it through a peephole, it cut off all of the object information and you’re only seeing the shadow on one side and the light surface on the other. The Spatial Context was removed and are not able to apply Top-Down Physical Regularity about how objects normally interact with light.

Question 61

___ information and our application of this heuristic of how light interacts with these different curvatures of surface can cause illusions in whether something appears to have a gradient or is homogenous.

Answer 61

Shape

Question 62

When the mist is white, you see black disks behind white mist When the mist is black/darker, you see white discs behind a black mist.
If you look carefully between the two, you’ll find the discs are identical, why did we perceive them as different colours?

Answer 62

In this case, the effect of the surrounding mist influences your percept of what these circles are showing

Question 63

There is an interaction between object processing and ___ processing.

Answer 63

lightness/colour