Laboratory of Cold Atoms Near Surfaces

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Camera obscura

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How to use a keyhole in an unusual way? Let's spy on... the world in the prototype of a photo camera.

More precisely, we take a look at camera obscura (pinhole camera). Usually one can construct it using a box in which there is a small hole in one side and a simple screen on the other side.

Shall the hole be really small? No! With a bigger hole (some 0.5 cm in diameter) we get a bright picture, in which even 2 mm objects might be visible.

How to prepare XL sized camera obscura? Sometimes we don't need to do anything — just look around and find it! Exemplary camera obscura found in a flat is shown below:

camera obscura scheme

If we have a door without glass in it and with a keyhole of a few mm in diameter, we get a clear image of the room and a window view on a wall of a neighbouring room — if only we darken it sufficiently. Exemplary image from such a camera obscura is shown below, taken with a digital camera (click the image to enlarge). The image was a few tens of cm wide. One can see a window, a railing and trees. In the right upper corner you see laces used to close the blinds. The diameter of the laces was 1.5-2 mm.

image in camera obscura

The original image was obviously inverted.


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(c) Tomasz Kawalec