P i n h o l e D r e a m s
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Principle of pinhole photography
A pinhole camera is a camera without any lens. The image is formed through a small hole at the back of a black box. Since light travels in a straight line, the pinhole image is inverted.
Pinhole diameter determines the image quality. If the hole is too large the resulting image is blurred. If the hole is too small, diffraction effects occurs and the image is also blurred.
The optimal diameter is a function of the distance between the hole and the image (the focal length). It is given in the following table.
Focal (mm) | Optimal diameter (mm) | Image circle (mm) |
30 | 0.21 | 114 |
60 | 0.29 | 228 |
100 | 0.38 | 380 |
Due to the small aperture of the pinhole camera, the depth of field is almost infinite. The image is entirely sharp (or nearly sharp) whatever the distance between the subject and the camera.
However, small apperture has also a drawback. The amount of light which goes through the hole is week. The exposure time is generally longer than with an ordinary camera.
People often feel that images produced by pinhole cameras are somewhat ghostly and delicate because of these two specific characteristics described previously
(c) JFD 2005