Jun. 13, 2011

Pinhole Viewer

by Science Friday Education

Click to enlarge images
Polaroid's 20x24 cameras, built in the late 1970s and named for the dimensions of their snapshots—20 by 24 inches, are the largest living Polaroid cameras in the world. (There was once an even bigger one with 40x80 snapshots, but the film has run out.) Five of these 20x24 cameras still exist, and one resides in New York City's 20x24 Studio. In the video below, the studio's director, artist John Reuter, and the director of photography, Nafis Azad, demonstrate the 235-pound camera, and Christopher Bonanos, author of Instant: The Story of Polaroid, explains how this camera fits into Polaroid's history.
In this activity, students will discuss and understand how cameras, telescopes, and their own eyes use light in similar ways. By building their own pinhole viewers, students will begin to make observations about the principles of light, and how design affects the quality of their observation tool.
Grade Level: 6th – 8th grade
Subject Matter: Physical Science
National Standards: NS.5-8.1, NS.5-8.2
Cameras, telescopes, and our eyes have many things in common, but the most striking is that all three require light to see or capture images.
Activity Materials
Toilet paper tubes – four for each student
Sheets of black construction paper – four pieces for each student
Rubber bands – eight for each student
Wax paper (cut into four by four-inch squares) – one square for each student
Tracing paper (cut into four by four-inch squares) – one square for each student
Tissue paper (cut into four by four-inch squares) – one square for each student
White plastic bag (cut into four by four-inch squares) – one square for each student
Aluminum foil (cut into four by four-inch squares) – one square for each student
Roll of Scotch or masking tape
Box of pushpins
Pinhole viewer: an optical device with a pin-sized hole that creates an image
Reflection: the change in the direction of light as it bounces off an object
Telescope: instrument used to look at distant objects
Retina: inner part of the eye that receives and transmits images to the brain via the optic nerve
Pupil: opening in the eye that regulates the amount of light that enters the eye
What To Do

1. Begin the lesson by having the students watch the Science Friday video, “Super-Sized Snapshot.” Ask students to describe what they saw in this video, and ask what differences and similarities they observed between a normal camera and the 20x24 camera they observed in the video. What additional special equipment did they need to make it work? How are the lighting requirements different for the 20 x 24 camera than a normal camera?

2. Ask students if they can compare how our eyes work to how a camera or telescope works. What is needed in order for any of these three to function properly? Allow students to share their ideas and suggestions with the class, before you mention that light is an important component in the proper functioning of all of these things. Inform students that by constructing pinhole viewers, they will observe the importance of light to making an image.

3. Hand out one toilet paper tube and one 4x4-inch square of wax paper to each student. Have students completely cover one end of the toilet paper tube with wax paper, and secure it in place with a rubber band. There should be very few or no wrinkles in the wax paper.

4. Instruct students to roll the piece of black construction paper to form an outer tube around the toilet paper tube, so that the toilet paper tube end that's covered in wax paper is inside the black construction paper tube. The open end of the toilet paper tube should be aligned with the end of the black construction paper tube. Students should secure the black paper with tape and label the construction paper tube, “Wax Paper.”

5. Have students cover the open end of the toilet paper tube with a square of aluminum foil, and secure it in place with another rubber band. Then they should use a pushpin to carefully poke a small hole in the center of the aluminum foil.

6. Have students label a clean piece of paper or a page in their science notebooks, “Pinhole Observations.” Underneath, they will record their predictions and observations. Ask students to start by predicting what they think they might see when they look through the pinhole viewers, and then have them record their predictions.

7. Take students outside with their pinhole viewers and observation sheets. Demonstrate how to use the pinhole viewer by looking into the open end of the black construction paper tube. Pinhole viewers work best in bright sunlight, by looking at a tree or roof line against the sky.

8. Have students look through the pinhole viewers and record their observations. They should include sketches whenever possible. Is the image clear? Is the image in color? Does the image appear right-side up?

9. Back in the classroom, ask students to share their observations. Were any predictions correct? Was anyone surprised by the results?

10. Tell the students that they are going to test various materials to determine which material produces the sharpest image in their pinhole viewer.

11. Hand out to each student three more toilet paper tubes and one square each of tracing paper, white plastic, and tissue paper.

12. Have students repeat steps 3 to 5 to create three new pinhole viewers. Make sure students label each new pinhole viewer with the corresponding material being used, i.e., “Tracing Paper,” “Tissue Paper,” “White Plastic.”

13. Repeat steps 7 to 8, with students using the new pinhole viewers to make and record their predictions and observations.

14. Have a class discussion on which material produced the sharpest image. Did everyone agree on which material was the best? What could be some possible reasons for the differences in the clarity of the image?

What’s Happening?
The time-lapse video, “Building an Observatory,” shows the construction of a dome that houses and protects a new planet-hunting telescope. This telescope, as well as the camera used to document the dome’s construction and the eyes that we used to view this time-lapse video, all work in similar ways in that they all require light. We cannot see without light reflecting off an object and entering our eyes. That is why we are not able to see in the dark if there is absolutely no light present.
When the light that reflects off an object enters our eyes through our pupils, the light travels through the different parts of our eyes and produces an upside-down image on our retina. The image travels to our brain through the optic nerve. Instead of seeing an upside-down image, our brain compensates by reversing the image so that it is right-side up. In a pinhole viewer, the light enters through the small pinhole, much the same way that light enters the eye through the pupil. The light creates an image on the wax paper, similar to the way that light creates an image on the retina of the eye. However, since a pinhole viewer lacks a “brain” to “fix” the image, it will appear upside down. The type of material that results in the sharpest image will vary, depending on the material being used. White plastic usually produces the sharpest image, but results may differ depending on the material used to make the white plastic bag, or on the other materials being tested.
Topics for Science Class Discussion
• What are some applications of pinhole viewers or cameras?
• What might happen if we try using our pinhole viewers on a cloudy day? At night?
• How do astronomical researchers use the telescopes at Lick Observatory to learn about the Universe?
Extended Activities and Links
Extend the activity by having students re-design their pinhole viewers so that they generate a larger image, or a more focused image or an image that is right-side up.
Challenge students to build a room-sized pinhole viewer in the classroom. Can they figure out how to create an image on the wall on the opposite side from a window?
Watch a video of an observatory being built, and discuss how the observatory and telescope are similar to a camera:
Have students research the history and science of photography online or at their local library.
Using the directions provided by Kodak, learn how to construct a camera obscura, an optical device that uses film to take pictures:
Visit artist Abelardo Morell’s website and view some of his creative photography using a pinhole camera:


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