The pinhole camera

The image now appears upside down and smaller on the transparent paper, and the image on the right can be seen on the screen in the setup on the left.

Now point the camera with the small hole in front at a bright object, e.g. a building brightly illuminated by the sun. A good alternative on cloudy days is to view several lamps through the pinhole camera. If you make the lamps distinguishable, e.g. by using colored foil, you can easily see the reversal effect in the image.

You can use either a tin can or a cardboard box as the camera body. The principle is identical. The following mainly describes the tin can camera. First, the inside of the tin can (or cardboard box) is lined in black. This can be done by inserting black drawing paper or painting the inside with black opaque paint. Now stretch the transparent paper tightly over the open side of the tin can or box and secure it with the elastic band (or adhesive tape). Then use the nail to carefully poke a small hole of about 1 mm diameter in the center of the bottom of the can (or the bottom of the cardboard box) so that light can pass through. The pinhole camera is now ready for use. You can make it even more sophisticated by protecting the focusing screen (the transparent paper) from light coming in from the side. To do this, roll a slightly larger piece of black paper around the tin can. For the cardboard version, throw a lightproof cloth over your head and cover the camera with it, as you would with the first cameras.

• a tin can or a small cardboard box,
• transparent paper (sandwich paper/parchment paper),
• black drawing paper,
• a large cloth that is as lightproof as possible,
• a nail,
• glue,
• possibly black opaque paint,
• 2 rubber bands,

What is technically behind the experiment

Light emanates from every point of the object under observation and travels in all directions. A tiny portion of this light passes through the aperture onto the ground glass and becomes visible there. Light coming from an upper object point falls on the lower area of the ground glass and vice versa due to the linearity of the light. This is why the image appears upside down.

What the experiment has to do with everyday life

In principle, our eyes function very similarly to a pinhole camera. Some simple animals have such simple eye types. In our eye, the lens also ensures that the image is always sharp, regardless of the pupil size. The tracing paper corresponds to the retina of the eye. The resulting image is also upside down in the eye, but is rotated in the brain - partly by an innate mechanism.

Nicole Schäfer & Sabrina Stark