Pinhole Camera

Part of Photography

A pinhole camera is the simplest possible photographic device — a light-tight box with a tiny hole that projects an image of the outside world onto a light-sensitive surface inside, requiring no glass optics.

Why This Matters

The pinhole camera is the first device you should build when beginning photography. It requires no glass, no precision machining, and no understanding of optics beyond a few basic principles. A functional pinhole camera can be built in a few hours from wood, a tin can, and a sewing needle — materials available in essentially any situation.

The pinhole camera teaches you everything about camera construction that applies to more advanced lens cameras: the importance of a truly dark interior, the relationship between hole distance and image sharpness, how to load and unload sensitive plates, how to estimate exposure, and how to use a shutter. These skills transfer directly to lens cameras, enlargers, and every other photographic device.

Practically, the pinhole camera is most useful for photographing subjects that are completely stationary — landscapes, buildings, documents, still life arrangements. Exposure times range from 1 minute to 30 minutes in typical light, which rules out people and animals but is perfectly adequate for surveying, architectural documentation, and copying printed material.

How Pinhole Imaging Works

Light travels in straight lines. A pinhole passes only the narrow beam of light aimed precisely at the hole from any given point in the scene. Light from the top of the scene passes through the hole and continues downward, landing at the bottom of the back wall. Light from the bottom of the scene passes through the hole upward, landing at the top. The resulting image is inverted — upside down and mirror-reversed.

The smaller the hole, the sharper each point in the image (because a smaller hole means a narrower beam from each scene point, producing a smaller dot on the back wall). But smaller holes also admit less total light, requiring longer exposure times.

There is an optimal pinhole size for each camera depth. Below this optimum, the wave nature of light causes diffraction that softens the image. Above it, the geometric blur from the finite hole size dominates. The optimum pinhole diameter for a camera of depth L mm is approximately:

d_opt ≈ 1.5 × √(0.0005 × L) (in mm)

For a 200 mm deep camera: d_opt ≈ 1.5 × √(0.1) ≈ 0.47 mm — approximately 0.5 mm. For a 100 mm deep camera: d_opt ≈ 0.33 mm.

Building the Camera Box

Materials:

• Wood planks, 8-12 mm thick
• Nails or wooden pegs
• Black paint or soot
• Thin metal sheet (tin can lid) for the pinhole plate
• A fine sewing needle
• Black cloth or felt strips
• A piece of glass slightly larger than the intended plate size (for the printing frame if needed)

Dimensions: Choose based on the plate size you will use:

• For 9 × 12 cm plates: interior 10 × 13 cm, depth 20 cm
• For 13 × 18 cm plates: interior 14 × 19 cm, depth 25 cm

The depth determines image size and exposure time. Longer camera = larger image = longer exposure. Start with 20-25 cm depth.

Construction:

1. Cut wood for six panels: front, back, two sides, top, bottom
2. Assemble with nails or wooden pegs. Glue all joints with animal hide glue or pine resin
3. Paint all interior surfaces flat black — multiple coats. Any reflective spot produces unwanted image flare.
4. In the front panel, cut a circular hole 10-15 mm in diameter at center
5. Cut a 3 × 3 cm square from a tin can lid
6. Using the finest sewing needle available, pierce one small hole through the exact center of the tin square. Aim for 0.3-0.5 mm diameter. Pierce once; do not enlarge by rocking the needle.
7. Mount the tin square over the wooden hole, pinhole centered, tacked with small nails
8. At the back of the box, build a plate holder: two thin strips of wood forming grooves that accept the plate, plus a dark slide (a thin wooden panel that slides in front of the plate)
9. Seal all joints inside and outside with thin cloth strips dipped in glue or pine resin
10. Light-tight test: seal up the camera, take it outside in bright sun, wait 15 minutes, open and inspect any loaded paper inside for light fog

Making the Pinhole

The pinhole is the most critical component. A rough, irregularly shaped hole produces a blurry or distorted image. The goal is a clean, round hole of the correct diameter.

Method 1 (needle in soft metal):

1. Anneal (soften) the tin piece by heating to dull red and quenching in water
2. Lay the tin piece on a piece of dense leather or hardwood
3. Hold the needle perpendicular to the tin surface
4. Press and rotate gently — do not push hard; let the needle pierce slowly
5. The hole should be clean and round with minimal deformation of the tin surface
6. File or sand the back of the tin flat to remove any protrusion around the hole

Method 2 (drilling in foil): Stretch very thin aluminum or tin foil over a hole. Use the finest drill point available, rotating by hand, to pierce a single hole.

Measuring the hole: Hold the pinhole plate up to a bright sky. You should barely see a bright point of light. If you can clearly see the hole as a bright spot without squinting, it is probably too large.

Compare against a set of calibration holes made by pushing the same needle into different parts of the tin with different amounts of force. Use the smallest hole that still allows some light to pass.

Loading and Using the Camera

Loading (in the darkroom under safelight):

1. Slide the dark slide out of the plate holder
2. Insert a coated glass plate or sheet of sensitized paper, emulsion side toward the pinhole
3. Replace the dark slide
4. The camera is now loaded

Exposure:

1. Set the camera on a solid support — a rock, a wall, a tripod. Any vibration during exposure blurs the image.
2. Aim the pinhole at the subject
3. Remove the dark slide halfway — this reveals the plate but does not expose it yet
4. Cover the pinhole with a small cap or piece of dark cloth
5. Complete removing the dark slide, verifying it is fully clear of the plate area
6. Begin the exposure: remove the pinhole cover and start counting time
7. At the end of the exposure, cover the pinhole
8. Replace the dark slide

Exposure times: These are approximate for gelatin bromide plates and a 200 mm deep camera with a 0.5 mm pinhole:

Conditions	Estimated Exposure
Bright direct sun, open landscape	15-30 minutes
Direct sun, building	30-60 minutes
Overcast sky	1-3 hours
Open shade	1-4 hours

Silver chloride paper (slower): multiply these times by 5-10.

Field Applications

The pinhole camera is ideal for:

Surveying and mapping: Place the camera on a hillside and make a 15-minute exposure. The resulting landscape image shows the surrounding terrain in natural perspective. Multiple images from known positions can be combined to reconstruct topographic relationships.

Architectural documentation: Photographs of buildings, fortifications, and structures for planning or historical record. The pinhole camera’s infinite depth of focus (everything is equally sharp from near to far, because there is no focus to miss) is an advantage here — no adjustments needed for different distances.

Document copying: Lay a document flat in bright sun, aim the pinhole camera at it from directly above, expose. Long exposure times are not a problem because the document is not moving.

Botanical and geological specimens: Arrange specimens in a well-lit frame and photograph from directly above. The long exposure is irrelevant; the subject will not move.

Multiple Pinholes and Special Effects

Multiple pinholes: A plate with two pinholes spaced apart creates two overlapping images that combine into one slightly blurred composite. This is generally undesirable but can be used artistically to show motion — if a subject moves between two successive exposures of half the normal time, both positions appear in the image.

Very long exposures: A pinhole camera pointed at the sky without a shutter, left for hours with a very slow emulsion, traces the arc of the sun across the sky as a single bright line — a solargraph. This technique shows day length and sun elevation throughout the day, useful for agricultural and architectural planning.

Panoramic pinhole: A curved back plate follows the geometry of a cylindrical panorama. If the back of the camera is curved to a radius equal to the camera depth, and the sensitive plate curves to match, a single exposure captures a wide panoramic field. Bend a sensitized paper strip into the curved back rather than using a flat plate.