The Camera Obscura
The video on the right shows a group of people attempting make a camera obscura in an office inspired by the work of Abelardo Morell. They make the room entirely light safe (completely dark) by taping black sheets to the windows. They then cut a small hole to let in a stream of bright light and an upside down image appears on the opposite wall. The reason this happens is because light travels in straight lines.
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This image helps to explain how this works. The light from the top of the object outside the window travels down through the hole to the bottom of the wall opposite. Similarly, the light from the bottom of the tree appears projected at the top of the wall, making the image appear upside down. Artists discovered this phenomenon hundreds of years ago and used it to help them create realistic images of the outside worlds on a two dimensional surface.
Here is a room sized camera obscura from the 18th century. You can see the screen onto which the image is projected inside the room.
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Here is an example of a portable wooden camera obscura from the 19th century. This uses a mirror system inside and a screen so that the image appears the right way round for the artists to trace.
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Abelardo Morell
Here are some images created by Abelardo Morell. They are made inside camera obscura using an SLR on a tripod with a very long exposure. It is important to use a tripod when the camera shutter is open for a long period because this ensures that the image stays still:
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My Camera Obscura
I decided to try to create two different kinds of camera obscura (fixed lens and telephoto lens) using the following materials:
Telephoto Lens Version
I began by cutting two lengths of tube of different diameters so that one could fit inside the other. I placed a small piece of greaseproof paper across the end of the thinner tube and taped it to the sides securely. I then attached a small piece of tinfoil over the end of the wider tube, taped it to the sides securely and made a tiny pin hole (about 0.5 to 1mm wide) in the tin foil. I inserted the thinner tube into the wider tube and moved it backwards and forwards noticing how the image increased and decreased in size. I adapted the camera by creating a special eye piece at one end to make sure that very little light got into the tube. The darker the tube inside, the brighter the image appeared. Fixed Lens Version This version was similar to the one above but a simpler construction. I used only one tube, cutting a section from the end over which I taped the tinfoil. I covered the longer section with greaseproof paper before re-attaching the shorter section. I made a tiny pin hole in the tinfoil and was then able to observe an upside down image projected onto the greaseproof paper screen inside the tube (see opposite). I was really pleased with my cameras. I preferred the telephoto version because it allowed me to zoom in and out of the image. However, the fixed lens version was also successful because I used a wider tube and the image was bright and clear. I am going to experiment with creating a slightly bigger camera obscura next time, possibly using my bedroom! |
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