The camera obscura was an invention that eventually led to photography. It is a box or a room with a hole on one side. A camera obscura is a simple optical device that projects an image onto a screen. Light from outside the box passes through the hole and lands on the flat surface opposite the hole. The scene outside is projected onto the screen inside the camera obscura, although the image is upside down.
What is a Camera Obscura?
According to Museum of Science Activities for Kids by Tanya Gregoire with Joan Parisi Wilcox (Adams Media Corporation, 1996), long ago, people would sit in a darkened room with a screen on one wall where a camera obscura would project images. Although this may sound like a trip to the movies, the camera obscura (meaning, “darkened room”) could only show what was going on outside the room.
If it was dark outside, this pinhole camera wouldn’t work, because it relied upon the light. This was at a time before movies, television, even photography, so it was a big deal for people to be able to see moving images.
How Does a Pinhole Camera Work?
A pinhole camera (a smaller version of a camera obscura) works because light travels in a straight line until it hits an object. When light hits an object, it reflects off that object’s surface. Some of the light travels through a tiny hole in the camera and projects an image on the back of the camera.
However, the image on the back of the camera will be upside down. Although light travels in a straight line, that straight line could be on a diagonal, so the light reflected from the bottom of an object will appear on the top of the camera’s screen. Build a pinhole camera and discover this for yourself.
Build Your Own Camera Obscura
You can build a pinhole camera within a few minutes. You just need a box that fits over your head with extra space (the sides of the box shouldn’t be too close to the sides of your head or your face). The box should be clean, have four flaps, and no holes or tears. If you have access to a box from a refrigerator or washing machine that isn’t ripped, you could try to build a camera obscura that you can sit inside.
Paint the inside of the box black and allow the paint to dry thoroughly. Cut a piece of white paper so it fits one side of the box and tape or glue it in place.
Ask an adult to help you take a knitting needle and poke a hole in the upper corner of the side of the box that is opposite the white screen. (Make sure that your head will not block the light that will come through the hole.) The hole should be no more than a half inch in diameter. Although a small hole creates a clearer image, because less light can go through the hole, the image will be dimmer.
Cut a hole in the bottom of the box that’s just big enough to slide your head through.
Use a Build Your Own Pinhole Camera
Put the box over your head so the small hole is behind you and the white paper screen is in front of your face. You may want to wrap a scarf around your neck to further block any light that enters from below. Take the camera outside on a sunny day. Aim the pinhole at an interesting scene, object, or action. You’ll see the image on the white screen – upside down.
After exploring how light passes through this simple camera, you may better understand why cameras have lenses that can control the amount of light that creates an image within the camera.
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