Science
University of Toronto Science of Colours Discussion

SCTM 2012

University of Toronto

SCTM

Question Description

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A cross-disciplinary approach in examining colour, with the aim of understanding colour from the multiple viewpoints of art, physics, chemistry, physiology and history.

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SCTM-2012 Science of Colours Winter Term 2020 Review Assignment Optional • Please upload all work to Canvas as a single pdf file. • Your name and student number should be clearly labelled on the front of the assignment. • Use diagrams and sketches to support your answer wherever it might be relevant. Review Assignment Due Wednesday April 1st SCTM-2012 - Science of Colour Part 1 OCAD University Question Points 1 1 2 1 3 2 4 3 5 2 6 4 7 4 8 4 9 8 10 2 11 4 12 3 13 4 14 4 15 4 Total: 50 1 of 7 Score Winter 2020 SCTM-2012 - Science of Colour Review Assignment Due Wednesday April 1st Question 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 points What colours have zero saturation? Question 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 points What kind of colour mixing do you suppose television and monitors use? Question 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 points What are complementary colours? Which ones are they? What kind of mixing this definition refers to? Question 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 points What colour would appear a white screen or piece of clothing if you illuminated it with (a) (1 point) Red light? (b) (1 point) Red and blue light, both with the same intensity? (c) (1 point) Red and blue light, and red light intensity is larger than blue’s? Question 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 points Identify on the colour triangle the achromatic point, defined as the locus where R = G = B. . Use the chromaticity diagram in figure 5 to help you to find the colours and show your answers in a colour triangle similar to the one shown in Figure questions 5 through 8. Question 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 points Identify on the colour triangle the following colours, given in 8-bit graphics specifications (a) (1 point) Magenta: R = 255, G = 0, B = 255 (b) (1 point) Cyan: R = 0, G = 255, B = 255 (c) (1 point) Pale yellow: R = 255, G = 255, B = 150 (d) (1 point) Pale pink: R = 255, G = 200, B = 200 Question 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 points Use the schematic chromaticity diagram in Figure 5 for the following problem: Four units of R, two units of G, and two units of B are mixed together. (a) (1 point) Find the colour coordinates of the mixture. (b) (2 points) Find the dominant wavelength and purity of the mixture. (c) (1 point) Find the dominant wavelength of the complementary hue of this chromaticity. OCAD University 1 of 7 Winter 2020 SCTM-2012 - Science of Colour Review Assignment Due Wednesday April 1st Question 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 points Using the colours in exercise 5, add together two pairs of light of your choice. Recall that when additively mixing two colours the resulting colour lies along the line connecting the two. (a) (11/2 points) Identify the resulting colours on the chromaticity diagram (colour triangle) (b) (1 point) Give their (r, g, b) fractions (c) (11/2 points) Show where the complements of these colours are on the triangle. Question 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 points (a) (2 points) Sketch reflectance curves for surfaces coloured with • blue • yellow (b) (2 points) Referring to your diagram in part (a), • describe how colour is mixed subtractively from these paints • what is the resulting colour? (c) (2 points) Sketch and label the sensitivity (or absorption) curves for the three types of cones (d) (2 points) • Describe how the colour obtained by additively mixing blue and yellow light can be predicted (Hint: use the diagrams you plot in part c). • What is the resulting colour? Question 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 points (a) (1 point) Define non-spectral colour. (b) (1 point) Why we see magenta, even though it is a non-spectral colour? Question 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 points (a) (2 points) Why do colours mixed additively not give the same mixed colour as those mixed subtractively? (Hint, think where the mixing process occurs: vision system or surface). (b) (2 points) Discuss the specific example of mixing red and green. OCAD University 2 of 7 Winter 2020 SCTM-2012 - Science of Colour Review Assignment Due Wednesday April 1st In the following graphs, a transmitance of 1 means that all the light of that wavelength is transmitted through the filter; 0.5 means that half of the light passes and 0 means that no light goes through at that wavelength. Question 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 points What colour is the light from (a) (1 point) filter A? (b) (1 point) filter B? (c) (1 point) filters A and B? Filter A 1 Transmitance Transmitance 1 0.5 0 400 500 600 0.5 0 400 700 wavelength (nm) Filter B 500 600 700 wavelength (nm) Figure 1 Question 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 points What colour would you see on the screen if you use filters A and B defined in exercise 12 in the configuration shown in (a) (11/2 points) left side of Fig. 2? (b) (11/2 points) right side of Fig. 2? In each case, briefly justify your answer. OCAD University 3 of 7 Winter 2020 SCTM-2012 - Science of Colour Review Assignment Due Wednesday April 1st W hit eL igh t Filter A t igh L e hit Filter B White Light W Filter A Filter B Screen Figure 2 OCAD University 4 of 7 Winter 2020 Screen SCTM-2012 - Science of Colour Review Assignment Due Wednesday April 1st Question 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 points Answer problems 12 and 13 using filters C and D, described below Filter C 1 Transmitance Transmitance 1 0.5 0 400 500 600 700 Filter D 0.5 0 400 wavelength (nm) 500 600 700 wavelength (nm) Figure 3 Question 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 points Show that using the simplified RGB spectrum and idealized reflectance curves the result of mixing (a) (1 point) cyan and magenta paints is blue, (b) (1 point) red and blue, is black. (c) (2 points) explain why is that (hint, see lecture 4) OCAD University 5 of 7 Winter 2020 SCTM-2012 - Science of Colour Review Assignment Due Wednesday April 1st 1 Fraction of green 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1 Fraction of red Figure 4: Colour triangle OCAD University 6 of 7 Winter 2020 SCTM-2012 - Science of Colour Review Assignment Due Wednesday April 1st Figure 5: Schematic chromaticity diagram, adopted from “The Physics of Music and Color” (Günther, 2012). OCAD University 7 of 7 Winter 2020 ...
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Final Answer

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SCTM-2012 Science of Colours
Winter Term 2020
Review Assignment
Optional
• Please upload all work to Canvas as a single pdf file.
• Your name and student number should be clearly labelled on the front of the assignment.
• Use diagrams and sketches to support your answer wherever it might be relevant.

Part 1
Question

Points

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1

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1

3

2

4

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5

2

6

4

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8

4

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2

11

4

Score

SCTM-2012 - Science of Colour Review Assignment Due Wednesday, April 1st

12

3

13

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14

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15

4

Total:

50

1 of 7

OCAD University

Winter 2020

SCTM-2012 - Science of Colour Review Assignment Due Wednesday, April 1 st

Question 1. (1 point). What colours have zero saturation?
Blue and Green
Question 2: 1 point What kind of colour mixing do you suppose television and monitors
use?
Red, Blue, and Green
Question 3: What are the complementary colours? Which ones are they? What kind of
mixing this definition refers to? (2 points).
Complementary colours are a combination of two colours (pairs) of colours that, when
combined, they lose hue. Thus, cancelling each other to produce a grayscale colour like
black and white. When the colours are placed next to each other, the colours create a sharp
contrast. The mixing is known as mixing hues of the colours.
Complementary colours:
✓ Red and Green
✓ Yellow and Purple(Violet)
✓ Blue and Orange
Question 4: What colour would appear a white screen or piece of clothing if you
illuminated it with:
(a) (1 point) Red light? White
(b) Red and blue light, both with the same intensity?

White light
(c) Red and blue lig...

jerryt (3645)
UC Berkeley

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