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You Can Make It On Your Own
  Teaching Guide

Activity 1: Grades 5-8
Red-Eye Reducer

Producing computer-designed objects is a reality in this MIT lab. Not limited to paper printouts, this laboratory system sends computer-assisted design files to a high-tech cutting machine. The machine reads the files and uses waterjet technology to cut designs into sheets of building material. The cut material can then be used to make devices from custom bicycles to red-eye reducing camera attachments.

Image of eye

National Science Standards and Curriculum Links
Print version (PDF)
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This activity page will offer:

  • Insight into the eye's anatomy
  • A chance to model red-eye reflection
  • A critical examination of red-eye elimination

Red-eye Model
In this activity, you'll create a model of an eyeball. By examining the structure of this body part, you'll create an understanding of why red-eye occurs. You'll even explore the angles of incoming light that may reduce this annoying byproduct of flash photography.


  • Round balloon
  • Paper mache paste (non-toxic paste obtained from art teacher)
  • Scrap newspaper
  • Non-toxic red paint
  • Paint brush
  • Gloves
  • Safety goggles
  • Scissors
  • Paper
  • Flashlight

    TEACHER NOTE: Scissors are sharp. Caution the students when using these tools. Review proper classroom behavior and techniques when using paper mache.


  1. Blow up a round balloon so that it is about 5 inches (about 12.5 cm) in diameter.

  2. Use scissors to carefully cut pieces of scrap newspaper into thin strips.
  3. Put on gloves and safety goggles. Soak the strips in paper mache paste. Review safety concerns associated with this step.
  4. Cover the balloons with two layers of soaked paper mache strips. Let dry. Then, add two more layers of soaked strips. Wait one day.

  5. Have your instructor poke a small hole into the dried paper mache covering. Remove the balloon through this hole.
  6. When the balloon is removed, have your instructor insert scissors into the hole and cut the dried paper mache cast in half, forming two hollow hemispheres.
  7. Then have the instructor use scissors to carefully cut out a coin-sized circular hole in the center of one hemisphere.
  8. Wearing both gloves and eye protectors, paint the inside of the both hemispheres red.

  9. When the paint has dried, use tape to secure these halves back into a complete sphere.

  10. Aim the beam of a flashlight directly into the opening. What do you see?
  11. Aim the beam at different angles into the eye. How does the angle of the light affect the observed red eye artifact. Which angles produce less red-eye reflection?



  1. Why was the inside of the eyeball model painted red?
  2. What does the coin-sized opening represent?
  3. How did the angle of the incident flashlight beam affect the red-eye property of the model?

Critical Analysis
Why does the angle of incident light affect the appearance of red-eye?

Anti Red-eye Strategy
One strategy for reducing red-eye uses a burst of flashes that occur just before the actual image is captured. Why would a burst of bright flashes reduce red-eye? Think about it and then present your ideas to the class. You may wish to share your understanding using your paper mache model.

Sell, Sell, Sell
Suppose you were in charge of marketing a red-eye reduction device that could be attached to any camera. How would you market this tool? How much of the science would you share with your audience? With access to computer graphics software, create a magazine ad that addresses the benefits and simplicity of your invention. If resources are available, script and shoot an "infomercial" that markets this device to the general public.

Web Connection
Anti Red-Eye Flash Photography

The physics of anti-red-eye photography as presented by a Mechanical Engineer.

Anatomy of the Eye

An introduction to eye anatomy that includes a QuickTime journey into the eye.

Waterjet Cutting

A primer on the science, history and application of waterjet cutting.


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