Atelier Bonryu(E)
double slit photography
Laboratory: Double Slit Photography
Feature of Double Slit Photography
The most important feature of the double slit photography is, as a matter of course, the distance between the vertical slit and the image screen is different from the distance between the horizontal slit and the image screen. By the way the vertical slit determines the angle of view in the horizontal direction, and the horizontal slit determines the vertical angle of view. In other words, the vertical slit determines the focal length of an image in the horizontal direction and the horizontal slit determines the focal length of an image in the vertical direction. Therefore, if the front slit is the horizontal slit and the back slit is the vertical slit, the horizontal angle of view is large and the vertical angle of view becomes small, which means that a photograph by this system is wide-angle-like in the horizontal direction and telephoto-like in the vertical direction, and vice-versa.
A projection of Mt. Fuji by a pinhole
A projection of Mt. Fuji by a double slit.
The upper left animation shows a projection of Mt. Fuji by a pinhole, by which “Sai-ana no Fuji (Mt. Fuji projected through a knothole) by Hokusai Katsushika” is reproduced. The upper right animation shows the same scene where a pinhole is replaced by a double slit. As the front slit is a horizontal slit in this case, projected Mt. Fuji is enlarged in the vertical direction, i.e., gets taller. It is understandable from the animation that unlike in the case of the pinhole photography, naturally, there is no point where all light rays pass in the case of the double slit. Though presently we use only a double slit system with a simple linear slits we can enjoy various changes in images by using slits with various shapes.
