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Calculating Color

In this lesson, students will learn about additive and subtractive color and how images are generated on screens and transferred to physical print. They will explore the difference between RGB (additive) and CMYK (subtractive) color models, and learn to count in hexadecimal numbers.

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Calculating Color

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  1. Calculating Color A lesson from TryEngineering.org Yvonne Pelham, IEEE Educational Activities Liz Kurzawa, IEEE Educational Activities

  2. Lesson Focus • In a digital world we take color for granted. Through off-computer activities, students learn the difference between additive and subtractive color, and how images are generated on screen and transferred to physical print. • Intended Ages: 11 – 13

  3. Educational Objectives Introduce students to: • How color is created on video screens using additive color. • How color is created in printers using subtractive color. • The difference between additive and subtractive color. • How and why additive color is represented as a single number.

  4. Learner Outcomes Students will demonstrate/explain: • How additive color (red, green, blue) creates color on a video screen. • How subtractive color (cyan, magenta, yellow, black) creates color in printers. • How to count in hexadecimal numbers. • How additive color is represented as a single number.

  5. Materials Session 1 • Red, green, and blue color gels, in sufficient quantities for groups of 3 -5 students to share one of each color • Three flashlights per group of 3 – 5 students • Rubber bands to attach gels to flashlights. • A set of used CMYB color printer cartridges.

  6. Materials Session 2 • Access to the Internet to watch videos, and to use an online color picker in groups of 3 – 6. • Magenta, yellow, cyan, and black washable paint. • 1 paintbrush per person. • Sufficient popsicle sticks for each group to share 8. • Art paper to draw upon. • Paper towels (for cleanup). • Newspaper to cover work surfaces. • 4 disposable bowls per team

  7. Additive Color • The colors red, green and blue (RGB) are used to produce colors on video screens (mobile phones, HD televisions) • A video screen has millions of little points of light called pixels. • Each pixel can be lit with a combination of red, green, and blue light. • When color and brightness are combined to produce a color, this is known as additive color. • Every pixel’s information is stored in the computer’s memory. The code that fills the screen with color runs through that memory grabbing one color at a time.

  8. RGB Example

  9. Hexadecimal Color • We count to 10 because we (most of us) have 10 digits (fingers) on our two hands. • In computers it is easier to count in hexadecimal or Base 16. • Since we need 16 digits to count in hexadecimal, we use the western alphabet to add digits. • RGB color is represented in hexadecimal or Base 16. • Using logic, the computer can quickly take this number and convert it into red, green, or blue, parts.

  10. Hexadecimal Example • In a hexadecimal number such as: FACA0B • The 2 left digits represent the red color. • The 2 middle digits represent the green color. • The 2 right digits represent the blue color. (RRGGBB)

  11. Converting Hexadecimal to Decimal #FACA0B • FA (red) = (F X 16) + A = (15 X 16) + 10 = 240 + 10 = 250 • CA (green) = (C X 16) + A = (12 X 16) + 10 = 192 + 10 = 202 • 0B (blue) = (0 X 16) + B = ( 0 X 16) + 11 = 0 + 11 = 11 • To convert to decimal (working from right to left): • (Bx160) + (0x161) + (Ax162) + (Cx163) + (Ax164) + (Fx165) = 16435723 • (11x160) + (0x161) + (10x162) + (12x163) + (10x164) + (15x165) = 16435723

  12. Subtractive Color • The primary colors in a color printer are magenta, cyan, yellow, and black (CMYK). • When color is transferred to a printed page, the colors are translated in combinations of the CMYK colors. • The color you apply to the surface absorbs some of the color and only reflects back the color you see. • It subtracts out the color that you don’t see, which is known as subtractive color.

  13. CMYK Color Example

  14. Session 1 Procedure • Invite students to bring in a colorful item from nature • Assemble students into teams • Review suggested video on additive and subtractive color (https://www.youtube.com/watch#sthash.1xvYPp63.dpuf) • Discuss how additive color is created on screens with pixels • Discuss how printer cartridges employ CMYK colors to create subtractive color, and if possible show actual cartridges. • Ask: • When you look at your found object are you seeing additive or subtractive color? • Predict which colors the objects are absorbing, and which colors are being reflected.

  15. Session 1 Procedure • Distribute worksheet 1 Invite students to: • Visit: http://www.rapidtables.com/web/color/RGB_Color.htm • Use the color picker tool to match the color of their object • Record both the hexadecimal and RGB color of their object • Use flashlights and color gels to match the color of their object • Distribute Worksheet 2 • Calculate each RGB color’s value from the hexadecimal number • Example: FA = (FX16) + A = (15X16) + 10 = 240 + 10 = 250

  16. Session 2 Procedure • Distribute Worksheet 3 • Distribute the following materials • Newspaper to cover work surfaces. • Four disposable bowls, filled with one each of the CMYK colors. • Two popsicle sticks per bowl to use to measure out paint. • One piece of art paper per student (have extras for restarts). • One paint brush per person.

  17. Session 2 Procedure Invite students to: • Enter their RGB colors into the RGB to CMYK converter: http://www.rapidtables.com/convert/color/rgb-to-cmyk.htm • Determine the percentages of Cyan, Magenta, Yellow and Black paint needed to create a 4X4 in (10X10 cm) swatch.

  18. Session 2 Procedure • Demonstrate how students can use the Popsicle sticks to estimate a measure of paint. • They will drop the estimated parts of paint onto their art paper • They should mark off and paint a 4”X4” inch swatch on their art paper and compare it with their found object color. • Students can then write their found object, the hexadecimal number, and the CMYK parts on the page • Each student’s entry can be used to create a class color wheel.

  19. Discussion 1)Was the color you produced a match with your found object? 2) If not, what colors did you to add in to get it right? 3) List the hexadecimal numbers for everyone in your group. Put them in order of smallest to largest. For example #3F4251 is smaller than #FACA0B. 4) What colors are stored as small numbers such as #00FFAA? Why? 5) What colors are stored as large numbers such as #FFAACC? Why? 6) What colors are stored as numbers in the middle and why?

  20. Next Generation Science Standards Grades 6-8 (Ages 11-14) Practice 2: Generating and Using Models • Develop and/or use a model to generate data to test ideas about phenomena in natural or designed systems, including those representing inputs and outputs, and those at unobservable scales. Practice 5: Using Mathematics and Computational Thinking • Use mathematical representations to describe and/or support scientific conclusions and design solutions. Practice 6: Constructing Explanations &Designing Solutions • Construct an explanation using models or representations

  21. Common Core Mathematics Standards All ages • CCSS.MATH.PRACTICE.MP1 Make sense of problems and persevere in solving them. • CCSS.MATH.PRACTICE.MP4 Model with mathematics. • CCSS.MATH.PRACTICE.MP5 Use appropriate tools strategically.

  22. Standards for Technological Literacy All ages • Nature of Technology • Standard 2: Students will develop an understanding of the core concepts of technology • The Designed World • Standard 17: Students will develop an understanding of and be able to select and use information and communication technologies

  23. CSTA K-12 Computer Science Standards Ages 11-14 • 5. 2 Level 2: Computer Science and Community (L2) • Computational Thinking: (CT) • 14. Examine connections between elements of mathematics and computer science including binary numbers, logic, sets and functions. • Collaboration (CL) • 3. Collaborate with peers, experts, and others using collaborative practices such as pair programming, working in project teams, and participating in group active learning activities. • Computing Practice & Programming (CPP) • 1. Select appropriate tools and technology resources to accomplish a variety of tasks and solve problems. • 2. Use a variety of multimedia tools and peripherals to support personal productivity and learning throughout the curriculum.

  24. Thank you! • Visit www.tryengineering.org for additional lessons • Questions? Contact: • Yvonne Pelham – y.pelham@ieee.org • Liz Kurzawa – e.kurzawa@ieee.org

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