The camera obscura is a very simple device that uses a lens to project an image on a screen. In Latin, the term “camera obscura” means “darkened chamber”, and it is indeed a small dark box with just a lens on one end and a translucent surface on the other. It was one of the inventions that led to photography.
I decided to make one as part of my experimentation in my university project. First of all, I needed to find a convex lens – the type that curved outwards rather than inwards (which is concave). I loaned mine at the workshop, but as an alternative, any magnifying glass will do.
Next, I have to determine the focal length of the lens. This could be easily done using a light source, such as a ceiling spotlight. Hold the lens on a table surface and move up and down until the light focused the sharpest on the table. The distance between the sharp focus (table surface) and the lens’ current position would be the focal length (just 2cm in my case); so, ideally the distance between the lens and the surface should be around this distance. To make it easier, it is better to have 2 parts for the camera so one end can slide in and out to focus.
For the front part of the camera with the lens, I just cut a hole slightly smaller than the lens. If the lens was mine I would have mounted it using glue, but since I will have to return it, I made a simple lens holder to slot it on the lens. Leave the other end of the box open for the back part.
The back part has to be a little smaller so it can be slotted into the front part. At one end of the back part, I used a translucent card but actually, anything similar that would let diffused light through will work. A simple alternative is tracing paper or maybe a piece of paper. Leave the other end open as well. (Ignore the gap, I didn’t have enough black card left.)
Finally, it’s time to put it all together! Slot in the lens into the holder and the back part into the front part.
Now, point the camera at anything and slide the two parts in and out to see the image forming on the surface! The image will appear inverted (upside down) because of physics, that’s a whole different story to tell!
But in the meantime, it is really cool to use this “grandfather of all cameras”; I did another version too with a mirror so the image appeared right side up!