Camera Obscura (Pinhole Camera)

This is a 4-H Solar Eclipse activity by Cynthia Canan, PhD, State 4-H STEM Specialist, Ohio State University Extension and Sara Newsome, 4-H Alumnus and STEM Student Assistant, The Ohio State University
Reviewed by: Wayne Schlingman, PhD, Director of the Arne Slettebak Planetarium, The Ohio State University, Sally Hennessy, Extension Educator, 4-H Youth Development, Ohio State University Extension-Lorain County and Katie Miller, Extension Educator, 4-H Youth Development, Ohio State University Extension-Shelby County

Topic: Space Science | Estimated time: 30 minutes | For individuals and groups (INTERMEDIATE to ADVANCED level) | PDF for PRINTING

NOTE: It is never safe to look at the sun without proper eye protection. The only time this changes is when the moon has completely blocked all parts of the sun during a total solar eclipse.

A total solar eclipse occurs when the moon passes between the sun and the Earth, completely blocking out the sun’s light. This occurrence is so amazing that millions of people around the world will travel to see a total solar eclipse. However, it is important to remember that proper viewing gear, such as solar eclipse glasses, is needed to protect your eyes. This is because staring directly at the sun can cause eye damage.

An easy way to prepare for viewing the eclipse is making your own cardboard box viewer. Cardboard box viewers project an inverted (upside-down) and reversed (left-to-right) image of the eclipse onto the cardboard so you can safely view it. But how do these cardboard box viewers work? In this activity, you will make a camera obscura, which uses the same principle as a cardboard solar eclipse viewer and can be used without the need of an eclipse.

This activity will also shed light on how your eyes work, which may be very different than how you imagined! If you want to make your own cardboard box viewer to prepare for the total solar eclipse, check out More Challenges!

NOTE: This activity will work best in a dark room where the only light source is from the activity.

Materials

• aluminum foil

• cardboard tubes (one paper towel tube or two toilet paper tubes )

• pushpin

• tape

• tracing paper, wax paper, or parchment paper

• optional: construction paper in a dark color

Be sure to complete this activity in a long space, such as a hallway or gym.

What To Do

Create your own camera obscura tube!

1. If using a paper towel tube, cut the tube one time to create ⅓ and ⅔ lengths. If using two toilet paper tubes, cut one tube in half. Keep one half and recycle the other half.

2. Cut tracing paper into a 3-inch square. Tape it so it covers one end of the longer tube.

3. Cut aluminum foil into a 3-inch square. Tape it so it covers one end of the shorter tube.

4. Tape the tubes together. The tracing paper should be between the tubes. The aluminum foil should face out.

5. Using the pushpin, gently poke a small hole in the center of the aluminum foil.

6. To decorate and decrease the light seeping into the taped sections, cover the entire tube with construction paper, but leave both ends uncovered.

Using Your Camera Obscura

NOTE: Our eyes need time to get used to the darkness of the camera obscura. Try closing your eyes for 30 to 60 seconds before opening one eye to look into the open end of the tube.

While outside, face the pinhole dot toward objects you would like to view that are getting direct sunlight. What do you notice about the images being projected onto your tracing paper screen?

Talking It Over

Write your answers to these questions and talk about them with your project helper or another caring adult. 

SHARE What images did you see through your camera obscura?

REFLECT How is a camera obscura different than a typical camera??

GENERALIZE Why do we use solar viewers to look at the sun?

APPLY How does the pinhole compare to a camera aperture (the camera’s lens opening)?

More Challenges

Create a cardboard box solar viewer to prepare for the day of the eclipse!
Watch this NASA video to learn how! youtube.com/watch?v=PI1ttQxXt5s

Remember to never look directly at the sun.

Background

A camera obscura is a dark space, such as a dark cardboard tube. Inside this tube, light rays can project an image of the outside world onto a screen, such as the tracing paper. To understand how camera obscuras work, think about how our eyes work to see objects in the world (Figure 1). Pretend you are outside, looking at a tree. You can see the tree because light rays from the sun are shining on the tree, and those light rays are reflecting (bouncing) into your eyes. These light rays are then focused to create a projection of the tree in the back of your eyes on a light-sensitive area called the retina. When light reaches the retina, it causes signals to be sent to your brain. Those signals allow your brain to understand the information and create the images you see.

A camera obscura works due to a similar concept of light ray reflection and projection. If you look at a tree through the camera obscura, the light rays reflect off the tree. Then the light rays enter through the tiny hole and project the image of the tree onto the tracing paper screen. Because our simple cardboard tube device does not have the same ability to focus light that our eyes do, using only a small pinhole to allow light rays into the tube forces the light to focus on a specific point. Look at Figures 2 and 3. Remember that light rays cannot bend and can travel only in a straight line.

In Figure 2, only certain light rays reflecting off the object can enter the “dark chamber” because of how small the hole is. In Figure 3, more of the light rays bouncing off of the same object can enter the “dark chamber” creating multiple projections and making the image look blurry. You can test this out yourself by making your pinhole bigger. If you decide to build a cardboard box, now you will know why we use a dark space and a tiny pinhole!

Did you know?

Camera obscura is Latin, translates to “dark room,” and is a sort of primitive camera and a starting point in photography.

Vocabulary

retina. The thin layer of cells lining the back of the eyeball in humans and some animals.

Learn more!

Turn your room into a camera obscura! Find out how at youtube.com/watch?v=gvzpu0Q9RTU.

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SOURCES

“How the Eye Works.” Cornea Research Foundation of America. cornea.org/Learning-Center/What-is-a-Cornea.aspx
“How Does a Camera Obscura Device Work?” HowStuffWorks. electronics.howstuffworks.com/question131.htm
“Camera Obscura.” University of Oxford History of Science Museum. hsm.ox.ac.uk/camera-obscura

Unless otherwise noted, all images provided by iStockphoto.com by Getty Images.

LEARNING OUTCOMES

Project skill: Learning how a camera obscura works | Life skill:Processing information | Educational standard: NGSS 4-PS4-2. Develop a model to describe that light reflecting from objects and entering the eye allows objects to be seen. | Success indicator: Builds a model to observe rays reflecting off an object to create an image

For more solar eclipse activities, visit go.osu.edu/4hsolareclipse.