Camera Obscura
The term "camera obscura" (Latin) means "dark chamber".

Centuries ago it was discovered that a small aperture would naturally form an image inside a dark space like a cave, tent or room. Since this is a natural phenomena, images were formed as soon as light appeared in the world! Artists would bring their materials into the camera to draw the surrounding scene in great detail and people would entertain themselves by watching the images move in real time (the first movies).

It's easy to make a Camera Obscura
Turning a room into a giant camera and watching the images inside is fascinating. It's quite easy and can be accomplished with recycled materials and tape.

For video clips & curriculim materials on the camera obscura and pinhole photography that Jim wrote at Tufts University's Wright Center for Science Education click here.


Ian Weir, a teacher at the University of Western Australia, made this photo inside a camera
obscura he created in a shearer's hut. He used a digital camera with a 5 minute exposure.



Step by Step Instructions
Choose a good room: The view outside the camera obscura should be bright. A higher interest level will be gained if there are objects moving in the view, such as vehicles, rivers, flags, clouds, people, etc. The outside should be accessible so that some of your people can go out and get into the picture themselves. It is a big advantage if the sun shines on the window. Make sure the room has adequate ventilation.

Cover the Windows: The space must be quite dark inside in order to see the image clearly. The room sized camera can also be used as a photographic darkroom for further study as long as there is no white light coming in. Many different materials can be used to cover windows. Small sections can be taped together. Black tape can be used to cover any small holes where light comes through. Here are a few materials that are inexpensive & easy to find:

Black plastic
Recycled cardboard boxes
Photo backdrop paper
Heavy duty aluminum foil
Black cloth
Wood panels
Window shades

In some situations you might have to put 2 layers on to achieve sufficient darkness in the room. If you want to use the room as a photography darkroom all sources of white light, even pinpoints, must be eliminated.


The use of new and old technologies leads to amazing results! Ian Weir used a light source to draw during the long exposure time required to make this digital photograph inside his camera obscura.



Aperatures let the light in
Apertures need an opening to be set into. Cut a 2 inch square pilot hole in the window covering.

How to make apertures
Simple materials can be used to make apertures, such as black paper, cardboard, aluminum baking pans or soda cans. They can be cut with a scissors, X-acto knife or drilled, depending on the capabilities of students and teachers. Metal apertures need to be sanded for safety to remove any burrs and sharp projections. An assortment of washers make excellent apertures. You can form apertures as small as 1/8 or 1/16 inch with no difficulty.

Basic apertures are round and the size of the apertures should vary. Common objects like coins can be used for reference sizes. Washers and other ready made objects will provide smaller apertures without the need for tools. The shape of the apertures can also vary. Try squares, rectangles, triangles, slits, stars, ellipses, etc. Make apertures with more than one opening!

Place apertures over the pilot hole on the window. Completely cover the pilot hole so that light only comes in through the aperture itself. To make this easier the apertures can be taped onto a sturdy paper or plastic mount.

Experiment! more than one pilot hole can be made to allow for more than one group to be active or to study the optical effects of multiple openings.

Mechanical apertures can be put to work, such as those from a view camera lens. Simply unscrew the lenses! Advantages: the size of the aperture is easily changed and there often is a useful shutter.


This aperture was formed with a coin and an x-acto knife.
A smaller one can be made with a hole punch. As shown
here, absolute perfection is not required to form a good
image in a large space!



Make a viewing screen
Viewing screens can be made from materials like tracing paper & drafting film. A translucent screen is often easier to use in demonstrations because the image can be viewed from behind the screen by everyone in the room. The screen material can be taped onto a frame cut out of cardboard, foam core, mat board or an existing picture frame.


A screen shows the image in Meg Ojala's camera obscura used in her photo classes at
St. Olaf's College.

 

Discussion of the Image
Once you have placed an aperture in the window and can see the image on the wall or screen the following questions can help you to understand what is physically happening in the camera. Start with an aperture about the size of a 5¢ coin for small rooms. Larger apertures, about the size of a 25¢ can be used for bigger rooms.

Where is the image formed?
Without a screen, the image is located on all the surfaces that the light encounters. A hand-held viewing screen will show that the image can be formed throughout the room.

How is the image oriented?
The entire image is upside down and backwards. Light rays from objects in the scene travel in straight lines through the aperture to form the image.

How sharp is the image?
Discuss the relative sharpness of the image, which changes with aperture size. Image sharpness generally increases as the aperture diameter diameter decreases.

How bright is the image?
It may take several minutes for your eyes to adjust to the light level in the camera. At first the image will be hard to see. After the eyes adjust it will be much easier to see the details. Brightness also changes with aperture size.

Is there any motion?
Objects moving outside will move in real time inside the camera. This happens at the speed of light! Students enjoy seeing each other run, jump, dance, etc.

What about colors?
On a white wall the colors are accurate but they will pick up the tint of other colors on the wall or screen.


A camera obscura can be made from a tent, car, big cardboard box, etc. The inside should be light in color for better viewing of the image, while the outside should be dark. Photo compliments of Meg Ojala


Activities for the Camera Obscura
• Pass a viewing screen around the room to show that the image forms almost everywhere. Try to find a place where the image does not form.

• Insert apertures of different size to show that image sharpness increases with smaller apertures and brightness increases with larger apertures.

• Change the distance from the screen to the aperture to show that angle of view increases as you approach the aperture.

• Different sized apertures will focus an image at different distances. Smaller apertures focus closer to the window.

• Send a group of people outside to clown around while those still inside watch. Continue until everyone has had a chance to participate.

• Put snow or water on the outside of the window and watch the movement in the camera. When things slide down the window they will be sliding up the wall on the image, seeming to defy gravity.

• Place a simple lens, such as a magnifying glass, over the aperture to see how a lens makes a sharper & brighter image. You’ll have to move the screen back and forth to find the correct focusing distance from the pinhole. The distance at which far away objects are focused by a lens is called the focal length of the lens.

• Try a simple experiment of your own choice.

 

More Developmental Activities
Basic Activities
• Make apertures with different shapes. Make apertures with more than one hole.

• Place the viewing screen at different angles to the axis of the aperture for ‘special effects’.

• Make a curved or bent viewing screen.

• Draw the projected image on a large piece of paper (a good group activity). Take the drawing outside and compare it to the scene. Objects outside that are close to the window will be magnified in the camera.

• Invite a photographer into your classroom.


Intermediate Activities

• Explore what kind of images form on the surface of different objects, such as a baseball, ice cream cone, glass of milk and found objects. You can cover the objects with white paper to see the image clearly.

• Place colored cellophane, gels or filters over the aperture to change the color of the image. Color mixing can be studied. For example, cyan + yellow = green.

• Draw portraits of people sitting outside the window.

• Use a mirror to redirect the image. How does a mirror change the orientation of the image?

• A mirror can also be used outdoors to direct sunlight through the aperture into the room. A bright beam of light will be formed that can be studied, redirected, bounced off successive mirrors or other surfaces, etc. The linear nature of the beam travelling through the dark space can be shown by clapping 2 erasers together to make a cloud of chalk dust. Thanks very much to Kendra Farrell and all her bright students in Freeport, Maine, who pioneered this excellent demonstration.

• Measure the angle of incidence of the sun (the angle between the sun ray and the floor).

• Make some photographs of the image inside the camera obscura.

• Will a tube form an image? Hold a bundle of straws together with a rubber band and place it over the opening in the window.

• Search the web for camera obscura installations.

• Take a trip to a camera obscura installation.


Advanced Activities

• Mark the location of the sun at different times of day. When the marks are connected you will have a ‘sun track’ for that day. If this is extended over a period of time you will be able to chart the path of the sun over the course of a season or year. This technique can be used to make a solar clock.

• Explore the optical properties of different lenses. Include image formation, focal length, combinations of lenses, etc. Encourage students to try their own ideas.

• Design and build a portable camera obscura room that can be carried from place to place. Cardboard and duct tape are the easiest materials to use.

• Design a system for determining the speed of objects outside the camera obscura using the image that is projected on the inside. Try cars, bikes, people walking, dogs, cats, ants, etc.

• Try this at night if you are in a dark neighborhood. Turn on the lights inside the camera obscura. Bring the viewing screen outside and hold it near the aperture. What do you think will happen? This activity turns space into a camera obscura and is a good analogy for microcosm & macrocosm.

• Make a camera obscura at home.

• Start a project to design and build a camera obscura in your community.

• Start a photography club.


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