Pinhole camera

A pinhole camera cannot provide high image sharpness. With a decrease in the diameter of the hole, the sharpness increases only to a certain limit, with too much reduction in the hole, diffraction effects begin to affect, the light on the hole and the image becomes less sharp.

The process of blurring an image is mathematically a convolution . The image on the screen is a two-dimensional convolution of the photographed object with a spot spread of a point light source ( English point spread function ), the image shape of a point light source in the case of geometric optics coincides with the enlarged hole shape (if neglected diffraction and other distortions). For example, if the hole has the shape of a slit, then the image of the point source will be a straight strip and the image of the scene will be linearly blurred; if several holes are made, the image will be “multiplied” (see also Coding Aperture ).

Obscura is characterized by infinitely great depth sharply depicted space . Talk about the focal length of the pinhole is only conditional. The equivalent focal length of such a camera is usually understood as the distance from the hole to the screen f . The f / D ratio is called, as in the lens, the Aperture Number . A camera with f = 100 mm and a hole diameter of D = 0.5 mm has an aperture value of f / 200. Increasing the hole (aperture) to 1 mm (two steps) reduces the number to f / 100. The exposure time is thus reduced to 25 days.

The first pinhole cameras were darkened rooms (or large boxes) with an opening in one of the walls. Mention of the camera obscura dates back to the 5th – 4th centuries BC. e. - The followers of the Chinese philosopher Mo-tzu ( Moists ) described the appearance of an inverted image on the wall of a darkened room ^[1] . Perhaps the mention of the pinhole camera is found in Aristotle , who wondered how a circular image of the Sun can arise when it shines through a square hole ^[2] .

In the X century, the Arab scientist Ibn al-Khaysam (Alkhazen) from Basra used special tents to observe the eclipses of the Sun. Knowing how harmful it is to look at the sun with the naked eye, he made a small hole in the tent canopy and examined the images of the sun on the opposite wall. Alkhazen was the first to explain the principle of the pinhole camera, based on the principle of the straightness of light distribution. At the same time, he concluded that the theory of the propagation of light generally accepted in those years (according to which light rays emanate from the eyes and “feel” the object, as it were) is not true.

In the Middle Ages, the pinhole camera was repeatedly used for astronomical observations. So, in the 13th century, the English philosopher Roger Bacon and the French astronomer Guillaume de Saint-Cloud used it to observe solar eclipses , the 14th century astronomers Levi ben Gershom and Ibn al-Shatir used a pinhole camera to measure the angular diameter of the Sun (in Levi ben Gershom - also planets).

Apparently, he was the first to use a pinhole camera for sketching from nature by Leonardo da Vinci . He also described it in detail in his Treatise on Painting . In 1686, Johannes Zahn designed a portable pinhole camera, equipped with a mirror located at an angle of 45 ° and projecting the image onto a matte horizontal plate, which made it possible to transfer landscapes to paper.

Some artists (for example, Vermeer ) used a pinhole camera to create their works - landscapes , portraits, household sketches. The pinhole cameras of those times were large boxes with a system of mirrors for deflecting light.

Isaac Newton in his monograph "Optics" describes the principle of operation of the apparatus similar to the camera obscura, but different device ^[3] .
In Russia, in the middle of the 18th century, a pinhole camera was spread, which was called "colossus for shooting perspectives." The viewer Makhaev, using the “colossus for removing St. Petersburg avenue”, made by the apprentice of “instrumental art” Tiryutin in the instrumental chamber of the Academy of Sciences, successfully performed promising views of St. Petersburg, Peterhof, Kronstadt and other Russian cities ^{[4] [5]} .

Often, instead of a simple hole, a lens (usually a single lens ) was used, which allowed to significantly increase the brightness and sharpness of the image. With the development of optics, lenses became more complex, and after the invention of photosensitive materials, pinhole cameras became the first cameras .

However, at present, some photographers use the so-called " stenopi " - cameras with a small hole instead of the lens. Images obtained using such cameras are distinguished by a peculiar soft pattern, an ideal linear perspective and an extremely large depth of field.

In the pre-photographic era, a lucida camera was also used, invented in 1807 by the English physicist Wollaston - a tetrahedral prism, at a certain angle of view, combining an imaginary image of a landscape with a sheet of paper on which a sketch is made.

• A pinhole camera is used for one of the murders in Henry S. Miller's Anamorph movie.
• The camera obscura is presented in Peter Webber’s film “ A Girl with a Pearl Earring ”.
• In one episode of the Heroes series, a woman watches a solar eclipse using this camera.
• In the series " White Collar " the main characters find such a camera obscura camera in an abandoned house.
• The pinhole camera was used in the cartoon The Simpsons .
• The pinhole camera was used in episode 7 of the 3rd season of Mad Men. In it, the heroes watched a total solar eclipse.
• One of Nabokov ’s novels is called the Obscura Camera .
• The pinhole camera effect was used in one of the episodes of Outland .
• There are pinhole cameras in the Turgor and Voice of Color computer games produced by Ice-Pick Lodge : if you touch any sister with color, the hero will see her real essence in the pinhole camera.
• The pinhole camera is often mentioned in Chuck Palahniuk 's novel The Diary.
• In the Da Vinci Demons series , Leonardo creates a pinhole camera and projects the image into the sky, thus blackmailing a high-ranking judge and thereby threatening to dishonor him in all of Florence with obscene behavior.
• The pinhole camera is featured in Steven Chbosky's film Miracle .

• During a partial solar eclipse , crescent-shaped shadows are observed on the surface of the earth. These shadows follow the shape of the sun , partially covered by the moon .
• Nautilus eyes work on the principle of a pinhole camera.

• Scattering spot
• Convolution (mathematical analysis)
• Coding aperture
• Stenop
• Dirkon
• Lucida chamber
• Pseudoscope

• Surdin V.G., Kartashev M.A. Camera obscura // Quantum. - 1999. - No. 2 . - S. 12-15 .

• Tomilin M. Obscura Camera (Russian) // " Soviet Photo ": magazine. - 1974. - No. 1 . - S. 42-43 . - ISSN 0371-4284 .

• Surdin V.G. Observation of sunspots with a classic pinhole camera.