Mechanics took its place in photography
Long exposure times didn’t require a shutter mechanism: a lens cap sufficed. But in order to make an exposure, lasting a fraction of a second, the use of a mechanism became essential. The first lens-mounted shutters appeared around 1860.
One of the first systems was the foreground shutter: a spring activated one or two valves. “In the case of instant photography” a drop shutter was recommended, which worked as follows: a blade with a hole in it slid into the frame with the help of gravity. A double guillotine perfected this system, moved by sideways-acting sets of springs.
Early shutters, experimental at best, were progressively replaced by various mechanisms offering a choice of different speeds and shutter actions. The roller-blind shutter located in front of the lens fully met these criteria, with the advantage that it was light and did not cause vibrations: the shutter was a sort of small blind made from black cloth which wound itself around a spring-loaded axle, whose tension could be adjusted according to the desired exposure.
From the 1900s on, two types of shutters became widespread: the focal roller-blind shutter situated in front of the sensitive surface, and the central shutter, which was made up of leaves exposing the lens from its centre outwards and mounted inside it. The Compur, which came out in 1912, was the most popular of these models.