Development of the Variable Aperture
December 28th, 2008
The earliest snapshot cameras had very simple lenses. They were designed for taking photographs in bright conditions. Anything other than bright sunlight or very light overcast conditions would make acceptable images unobtainable without flash or some other form of artificial lighting.
This was all very well, but what if you wanted less light in the camera? What if it was too bright? Letting too much light in would overexpose the film. One solution would be to put a neutral density filter over the lens each time but this is cumbersome, inconvenient and unwieldy.
Luckily, the precursors to modern cameras were developed with an addition built into the lens - the diaphragm. This is a device to give a variable sized hole, or aperture, in the centre and therefore allow more or less light in. In this way, the aperture controls the amount of light coming into the camera and can be altered according to the light levels in the scene selected.
From that moment it was extremely easy to consider producing images from scenes as diverse at midday sunshine and gloomy interiors. And all this without the need for either artificial light or some external way of blocking excessive illumination. Developers carefully assigned numerical values to apertures sizes which became the “f-stop” notation the larger the f-number the smaller the aperture.
Eric Hartwell runs the photography resource site http://www.theshutter.co.uk and the associated discussion forums as well as the regular weblog at http://thephotographysite.blogspot.com
Entry Filed under: The Photographer's Way