Pinhole Camera

A pinhole camera is a simple photographic device that operates without a lens, using instead a tiny aperture through which light passes to form an image. Constructed as a lightproof box with a small opening on one side, it projects an inverted image onto the opposite inner surface. This projection process reflects the camera obscura effect, a foundational principle in optics. Image characteristics depend largely on the distance between the aperture and the image plane, and the technique has become popular both artistically and educationally. Worldwide Pinhole Photography Day is celebrated annually on the last Sunday of April, highlighting the continued relevance of this ancient imaging method.

Historical Background

The origins of the pinhole camera lie in the camera obscura, a natural optical phenomenon described in early Chinese texts such as the Mozi writings around 500 BCE. Aristotle also referenced the behaviour of light passing through small apertures in his Problems circa 300 BCE. By the medieval period, scholars such as Ibn al-Haytham (Alhazen) provided detailed explanations of the camera obscura effect, particularly its ability to project an external scene into a darkened chamber.
From the Renaissance onward, experimenters refined the device for practical study. Giambattista della Porta’s Magia Naturalis (1558) described using a concave mirror to enhance image projection for drawing aids. Around the same time, lenses began to be incorporated, improving sharpness and brightness. By the seventeenth century, camera obscuras equipped with lenses had evolved into portable structures such as tents and wooden boxes used by artists. The first photographic cameras of the nineteenth century were direct developments of these box-type devices.
The term “pinhole” appeared in James Ferguson’s 1764 book Lectures on Select Subjects in Mechanics, Hydrostatics, Pneumatics and Optics, marking the adoption of the concept within optical science.

Early Pinhole Photography

The first written description of pinhole photography appeared in David Brewster’s 1856 work The Stereoscope, where he outlined the idea of capturing images without lenses. Later, Sir William Crookes and William de Wiveleslie Abney experimented with pinhole image capture, contributing early examples of practical pinhole photography.
Experiments related to moving pictures also involved early pinhole-like approaches. Around 1887, Thomas Edison’s team initially attempted to create microscopic pinpoint photographs on a cylindrical shell, intended to synchronise with phonograph recordings. The technique was quickly abandoned due to low image quality and limitations in emulsions, leading to the eventual adoption of lenses in the Kinetograph camera by 1893. In the realm of integral photography, Eugène Estanave used pinhole principles in experiments during the 1920s, later adapting his work after 1930 by replacing lenticular screens with pinholes.

Applications and Usage

Pinhole cameras can be used in several ways depending on educational, artistic or scientific objectives. When equipped with a translucent screen, they allow real-time projection of images and are frequently used for safe solar eclipse viewing. Without a screen, they function as photographic cameras, exposing either film or photographic paper. This mode is common in long-exposure photography, including solarigraphy, which records the Sun’s path across months.
Key uses include:

• artistic long-exposure imagery
• educational demonstrations of optical principles
• surveillance applications using pinhole cameras with CCD sensors, valued for their discreetness
• scientific or experimental photography in which wide depth of field and distortion-free images are preferred

Several related devices have been developed from pinhole principles, such as Franke’s wide-field pinhole camera, the pinspeck camera, and the pinhead mirror. Advances in manufacturing have made high-quality, laser-etched pinhole apertures widely available for use with digital cameras.

Construction Techniques

Pinhole cameras can be easily handmade, offering flexibility for custom purposes. The basic construction consists of a light-sealed box with a pinhole at one end and a light-sensitive surface at the other. Cylindrical containers, such as empty cans with detachable lids, can be repurposed effectively. The pinhole is often created by puncturing aluminium foil or thin brass using a fine needle; the resulting metal square is secured behind a larger opening in the box. A small flap made of card, fixed with tape, functions as a shutter.
Key construction considerations include:

• painting the interior black to minimise internal reflections
• ensuring the pinhole is clean, circular and free from burrs
• maintaining a rigid structure to prevent light leaks
• using sliding film holders to vary the distance between aperture and film, thereby altering focal length and field of view

A shorter distance creates a wide-angle view with reduced exposure time, while a longer distance results in a telephoto effect requiring significantly longer exposure. Conventional cameras with damaged lenses can also be revived as pinhole cameras by replacing the lens assembly with a pinhole, allowing continued use of shutters and film advance mechanisms. Digital SLR users often adopt commercial pinholes to experiment with exposure and composition without film development costs.

Optimal Pinhole Size

The quality of a pinhole image depends critically on the aperture diameter. A smaller pinhole yields sharper images but reduces brightness. If the hole becomes too small, diffraction softens the image, creating a balance point determined by optical theory. The aperture should ideally be less than or equal to approximately one-hundredth of the distance between the pinhole and the image plane.
Key optical considerations include:

• excessively small pinholes increase diffraction blur
• overly thick materials introduce vignetting as the sides obstruct oblique rays
• perfectly round holes produce more uniform diffraction patterns

Laser-etched industrial pinholes provide exceptional consistency, though skilled hobbyists can produce satisfactory results using thin foil.
Several formulas have been proposed for determining optimal pinhole diameter. Joseph Petzval’s 1857 calculation was among the earliest, based on minimising the size of the projected circle of confusion. Later, Lord Rayleigh offered an alternative in 1891, though some assumptions led to slightly larger recommended diameters. Young’s 1971 proposal derived from Fraunhofer diffraction suggested a simplified formula:d ≈ 0.0366√fwhere d is the aperture diameter in millimetres, f is the distance to the film plane in millimetres, and the wavelength of light is assumed to be 550 nm (yellow–green light).