岡本明才Meisai Okamoto
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PINHOLE CAMERA / CAMERA OBSCURA

What Is a Pinhole Camera?

A pinhole camera forms an image using light passing through a small hole instead of a lens.

INTERACTIVE / PINHOLE

How Do Box Length and Hole Size Change the Image?

Pinhole ray diagramLight travels straightPerson upper point: red, solidPerson lower point: blue, dashed
Pinhole ray diagramA ray diagram with one person left of the optical axis, showing red light from the person’s upper point and blue light from the lower point following separate straight paths through the top, centre and bottom of the opening, swapping sides and forming separate red and blue footprints on the projection surfacePersonProjected-image visualizationA person-only inverted image whose scale follows box length, showing three representative copies through the top, centre and bottom of the opening plus the continuous geometric overlap of image points, with diffraction added separately for extremely small holesProjected-image visualizationInverted imageReflected light spreadsStraight through top, centre and bottomOne object point becomes a footprintBars = one-point widthPinholeProjection surfaceBox length

Three representative aperture paths With a large opening, overlap between neighbouring image points is emphasized until the person’s shape becomes unreadable. Numerical values remain physically calculated.

This is a lensless pinhole model. Even light from one point on the person follows separate straight paths through the top, centre and bottom of the opening and reaches slightly different places on the screen. A small hole makes a narrow footprint with less overlap; a large hole makes neighbouring image points overlap and look blurred.

Projected image height
68.0 mm
Magnification
0.040×
Effective f-number
f/356
One-point footprint (geometric)
0.47 mm
Diffraction blur
0.48 mm
Combined blur estimate
0.67 mm

Why does a larger hole blur the image?

01Every point that forms the person reaches the projection surface as a small patch. With a small hole, those patches are narrow and neighbouring points mix less, so the outline looks sharper.

02A wider hole does not make one ray thicker. Separate straight paths from the same point pass through different parts of the hole, cover a wider patch and overlap neighbouring image points, softening the outline.

03After passing through the opening, the rays do not converge; each continues along the same straight line. Moving the projection surface farther from the hole makes the top and bottom rays land farther apart, enlarging the image.

04An extremely small hole, however, increases diffraction blur. The smallest opening is not always the sharpest.

Approx.. The person’s distance is compressed to fit this schematic. The three red and three blue rays represent the continuous paths through a circular opening; the screen bars and three person copies enlarge the footprint for legibility. A real point spreads as a circular patch on the image plane. Large-opening projection blur is emphasized non-linearly to communicate the continuous overlap of image points, while the displayed numbers remain physically calculated. Magnification uses box length divided by subject distance; geometric blur follows the finite opening, and diffraction is estimated for a circular aperture at 550 nm. Brightness, exposure time, reflectance and recording-medium response are not simulated.Model basis: similar triangles and a circular-aperture diffraction estimate

Pinhole camera: a 3D explanation

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A 3D view follows light reflected from points on a tree through a small hole to an inverted image. It compares how small and large openings change each point’s footprint and the clarity of the image.

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Sunlight reaches the tree and reflects from each point on its surface in many directions. Different colors distinguish light from the top, middle and bottom of the tree. The rays spread in depth as well as across the screen.

A dark box with a small opening stands between the tree and the screen. Light that strikes the wall stops there; only the portion directed toward the opening enters. Light from different points passes through at the same time. The opening neither bends nor converges the rays.

Light continues straight after passing through the opening. Light from the top of the tree reaches the bottom of the screen, light from the bottom reaches the top, and light from the middle reaches the middle. The resulting tree image is inverted vertically and horizontally.

The viewpoint travels along the light path: from the sun to the tree, from reflection at the tree toward the opening, and through the opening to the screen inside the box. Outside and inside views show that the path remains straight.

With a small opening, light arriving from one point on the tree makes a small circular footprint on the screen. More footprints, corresponding to different points, gradually appear and combine to form the fine outline of an inverted tree.

The opening grows while the tree and screen stay in place. The footprint from the same point becomes larger. Large footprints from many points overlap and blur the outline. The final side-by-side comparison connects the size of each footprint with the appearance of the whole image.

The rays and opening are enlarged schematic representations, and the circles explain how the image forms. Brightness is adjusted for the comparison. A smaller opening does not make the image indefinitely sharper: diffraction also causes blur when the opening is too small.

A pinhole camera is one of the simplest photographic devices. Instead of a lens, it forms an image from light entering through a tiny aperture. Because it relies directly on light traveling in straight lines, the image emerges through specific conditions: aperture size, distance and time. This page considers pinhole photography and the relationship between the pinhole camera and camera obscura through principle, structure, history and expressive possibilities.

01 / PRINCIPLE

How a Pinhole Camera Works

A pinhole image is created as light travels in straight lines through the aperture and is projected onto a surface. A larger aperture admits more light but produces a softer image. Reducing the aperture tightens the image within a certain range, but requires a longer exposure; if it becomes too small, diffraction softens the image again. This trade-off between brightness, sharpness and time is fundamental to the pinhole camera.

Aperture diameter
Affects image sharpness and brightness
Projection distance
Affects image size and brightness
Exposure time
Determines whether the image can be formed
Fading Light, an artwork with blue light and a white circular image in darkness
Fading Light / 2021

02 / DEFINITION

Definition of a Pinhole Camera

A pinhole camera forms an image with light passing through a small aperture instead of a lens. Unlike conventional cameras optimized for sharpness, a pinhole camera makes the conditions of image formation—exposure time, aperture diameter and subject distance—especially visible.

It can therefore be treated both as photographic equipment and as an apparatus for observing the behavior of light and the assumptions behind vision.

03 / STRUCTURE

Minimum Structure

A pinhole camera has three essential elements.

  1. 01A light-tight box: a space that controls light
  2. 02A pinhole: the entrance for light
  3. 03A light-sensitive surface: film, photographic paper or an image sensor

This structure can be enlarged easily. A larger box becomes a giant camera; if a building or room is made light-tight and an aperture is opened, the space functions as a camera obscura.

A photographic apparatus built from cardboard
Cardboard Digital Camera No. 3 for heuristic, 2011

04 / CAMERA OBSCURA

Relationship to Camera Obscura

A camera obscura projects the scene outside onto a surface inside a darkened room or box. It can use a small hole or a lens.

A pinhole camera forms an image through a small hole instead of a lens. It shares its principle with a lensless camera obscura, but either can take the form of a box or a room, so size or portability alone does not distinguish them.

The apparatus used to make Corridor of Time
Camera for Corridor of Time, 2006

05 / HISTORY

A History of the Pinhole Camera

The observation that an aperture forms an image was recorded more than two thousand years before photography. The essentials are below. The full fourteen-stage chronology, eight side stories and twenty-four sources are gathered on a separate page.

  1. c. 4th–3rd century BCE

    The MoziLight crosses at a small aperture; the image is inverted

  2. Early 11th century

    Ibn al-HaythamDescribes image formation through a small aperture in a dark space

  3. 1544

    Gemma Frisius observes an eclipsePublishes the projection into a darkened room as an illustration

  4. c. 1826–1827

    NiépceKeeps a projected image permanently — photography begins

  5. 1890

    George DavisonPinhole photography is recognised as expression

Read the full history of optics before photography

06 / EXPRESSION

Pinhole Photography as Expression

Pinhole photography is more than simply “retro” or “soft.” By stepping away from the lens-based values of resolution and focus, it can make the conditions through which an image appears into the subject of the work itself.

  • The image appears as a set of conditions: time, distance and aperture
  • The idea of a single focus weakens and the space becomes more even
  • Designing the apparatus becomes part of the act of making

07 / FAQ

Frequently Asked Questions

How does a pinhole camera work?

Light travels in straight lines through a small hole and projects an inverted image on the inside of a dark box. Reducing the hole tightens the image within a certain range, but it admits less light, so the exposure takes longer; if the hole becomes too small, diffraction softens the image again.

Can I make a pinhole camera myself?

Yes. A pinhole camera can work with three elements: a light-tight box, a pinhole and a light-sensitive surface. The precision of the aperture and the exclusion of stray light are essential to a stable image.

What is the difference between a camera obscura and a pinhole camera?

A camera obscura projects the scene outside onto a surface inside a darkened room or box, and some versions use a lens. A pinhole camera forms its image through a small hole instead of a lens. Size alone does not distinguish the two.

Why do pinhole photographs look soft?

With a larger aperture, light from multiple directions overlaps and softens the image. Reducing the aperture tightens the image within a certain range, but an aperture that is too small introduces diffraction and softens it again. A small aperture also admits less light, requiring a longer exposure and increasing the effect of movement.