Camera ObscuraGo into a very dark room on a bright day. Make a small hole in a window cover and look at the opposite wall. What do you see? Magic! There in full color and movement will be the world outside the window — upside down! This magic is explained by a simple law of the physical world. Light travels in a straight line and when some of the rays reflected from a bright subject pass through a small hole in thin material they do not scatter but cross and reform as an upside down image on a flat surface held parallel to the hole. This law of optics was known in ancient times.
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What is Camera Obscura? |
The first type of camera ever invented was called a camera obscura, which is Latin for 'dark room.' At first, that's exactly what it was - a dark room with a tiny hole that allowed a narrow beam of light to enter. This beam produced a 'real image' of outside objects on the wall opposite the hole (it didn't take pictures, though - light-sensitive materials like film weren't invented until much later). A pinhole camera is just a portable version of this ancient camera obscura. (It's a bit inconvenient to carry a room with you to take pictures of your family vacation!)
In a modern camera, a lens is used to bend light waves into a narrow beam that produces an image on the film. In a pinhole camera, the hole acts like a lens by only allowing a narrow beam of light to enter. It forms the same type of upside-down, reversed image as a regular camera, so you can see how a camera works by making a pinhole viewer. (Read more about how cameras work here.) With photographic paper and the right developing materials, you can make a pinhole camera that will actually produce photographs. In this project, though, you'll make a pinhole camera viewer that allows you to see a real image, but not record it. |
Pinholes |
If you make the pinhole too big, you allow too much light in and your lose the rays-in-parallel effect (and your image becomes very blurry because now all those rays of light bouncing off your subject are overlapping each other on the focal plane). If you make the pinhole too small then not enough light is able to enter the camera body and your image cannot be properly exposed.
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