The Camera Obscura

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All our modern cameras have one common ancestor - The Camera Obscura: the light of the outside world falls through a pinhole onto the opposite wall of a room and produces an upside-down picture. In the 16th century the camera obscura was greatly improved by an objective lens, which produced much brighter pictures and around 1750 many painters, like the Venetian Canaletto, used it to make sketches for their paintings. Then in 1836 Nicéphore Nièpce projected the picture on a light-sensitive plate and the photographic camera was born.

Our beautiful, sturdy Camera Obscura is equipped with a powerful lens (60mm diameter, 275mm focal length) and a mirror for an upright picture, like the one Canaletto used. The picture is projected onto a 16x16cm screen with transparent paper on which it can be viewed or copied by pencil.

Pre-punched kit with gold printing,
complete with lens, mirror,
clear screen and transparent paper.

Size: 280mm x 190mm x 190mm

The principle of the camera obscura (dark room), the forerunner of all our photographic and video equipment, is surprisingly simple. In a darkened room, a small hole in one wall produces an inverted image of the scene outside, on the opposite wall. The image is not very bright since the small amount of light that comes through the hole is spread over the whole wall, but when the eye has adapted to the dark, the image appears as if by magic. The room could be a whole room in a building or simply a box in which the projection wall is replaced by a matt plate so that the image can be seen from outside the box (see the sketch). We must suppose that humans in pre-history times noticed that a small hole in the curtain in front of the cave entrance would project the landscape into the cave interior. This would make the camera obscura man's oldest optical device.

Aristotle (384-332 BC) was the first person to investigate this scientifically, and Leonardo da Vinci discovered that it also occurs as the optical principle in our eyes (and those of most vertebrate animals). The images on the retina of the eye are in fact upside down. We see them the right way up because of corrective action by the brain.

The pinhole camera. as the camera obscura is also called when it is not using a lens, is governed by two laws.
1. The further the projection screen is from the opening where the light enters, the larger is the image, but it is also dimmer.
2. The larger the light-entry opening, the brighter is the image, but also the less sharp.

This has greatly limited the possibilities for using it, e.g. to observing very bright objects such as the sun during eclipses. The problem was not solved until the 16th century, when for the first time ground lenses were used in place of the hole, making the image sharp ("focusing").

However, even such a focusing camera obscura has a disadvantage: The lens cannot show all objects at different distances equally sharply; it needs to be focused by pulling it out for near objects and pushing in for distant ones. In contrast, a pinhole camera shows all points of the image equally sharp.

In 1686, Johann Zahn made the first camera obscura that, with the aid of a mirror, made it simple to draw pictures of the subjects. It subsequently became popular with painters, who could use it as an easy way to determine the correct perspective for their pictures. There are well known almost photographic paintings by the Venetian Canaletto from around 1750 (in, for example, the National Gallery in London and the Old Masters gallery in Dresden), who used a focusing camera obscura for this work.

This Astro-Media kit works on exactly the same principle. Photography was born when the Frenchman Nicephore Niepce shortened this path by capturing the image directly on a light-sensitive plate. The

camera obscura lives on in the millions of still and video cameras that we have today. However, there are today still some genuine examples of the camera obscura at tourist attractions. A large darkened room in which a mirror in the roof casts the image onto a projection table where whole groups can

view it.