Pinhole photography is the most basic optical system, using no lens, but a tiny ‘pinhole’ aperture punched in a metal plate fixed to the front of the camera. Its precursor was th camera obscura, dating from the 10th century and adapted as an optical aid for artists in the 1540s. From the 1850s, pinhole apertures were used in experimental photometry, assessing lens distortion and spectral absorption, but were rarely applied to photographic imaging until after 1880. The reasons for this concern the particular optical properties of a pinhole which, as compared with a lens, produces substantial diffusion and requires very long exposure times. Unlike a lens, an aperture cannot bend the rays of light to focus an image on the receiving plane, but instead simply allows a bundle of light rays to pass through it. Poor image resolution results, although it can be improved by radically restricting the size of the aperture. Yet this operates only to a degree, because a very small aperture produces diffraction, which itself undermines resolution. Furthermore, at a small aperture, fewer light rays will reach the receiving plane, necessitating long exposures, and pinholes were not practicable for imaging until photographic negatives were made more light sensitive.
A pinhole aperture dispensed with lens aberrations, and was recommended for architectural work, as no curvilinear distortion was produced. Depending on the distance from aperture to image plane, the pinhole camera also gave a wide angle of view and nearly infinite depth of field. Even the soft focus of the images was appreciated, for diffusion was an aesthetic championed since the 1840s as being akin to natural human vision. Indeed, the pinhole camera was thought to be a more direct means of imaging, and an early term for the device was the ‘natural camera’. In the early 1890s, some photographers associated the pinhole's uniform diffusion with the principles of impressionism, arguing that this approximated the mind's synthetic analysis of optical sensation.
Pinhole cameras were manufactured in the USA from 1887 and in France from 1888. Though often dismissed as cheap amateur toys, they were also valued as a practical riposte—made by domestic craftsmen—to the elaborate devices of the photographic industry. Indeed, the long exposure times were welcomed as a contemplative antidote to instantaneous photography and the tumult of Victorian life. ‘To get the largest amount of enjoyment out of pinhole photography’, wrote H. H. O'Farrell in 1887, ‘you must set your camera … at dewy morn before some old ruin that will keep still without a head-rest, and linger on till the lengthening shadows and the sinking sun warn you that night is at hand.’.
Given the simplicity of lensless photography, there was little scope for technical improvement. In 1890, Sir William Abney experimented with a diffraction grating, and in 1892, Alfred Watkins published a system of calibrating exposure to aperture size. More extreme diffusion was obtained through the use of a slit aperture, though the resulting astigmatism led dizzy viewers to dub this approach the ‘nauseagraph’. At the beginning of the 21st century, pinhole imaging in its basic form is practised by enthusiasts; but it also has relevance to astronomy and nuclear physics, and is used in ever more innovative circumstances.
— Hope Kingsley
See also zone plate.Bibliography
- Kraszna-Krausz, A. (ed.), Focal Encyclopaedia of Photography (rev. edn. 1960).
- Renner, E., Pinhole Photography (2nd edn. 2000)
