Beverage cans can record photographs when you give them darkness, light-sensitive paper, and a little patience. So how do you make a photograph without a camera?

This method needs no conventional camera or lens, although your homemade container becomes a camera itself. The essential ingredient is a tiny opening that lets light form an image inside a dark box.

We can start with this simple trick, then build something that records it.

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Key Takeaways

• A pinhole camera is a light-tight box with a small opening. Light passes through the hole and projects an inverted image onto photographic paper or film.
• Pinhole size affects both sharpness and exposure: a smaller hole admits less light, while an extremely small hole can soften detail through diffraction. The distance between the pinhole and recording surface affects the f-number and angle of view.
• A homemade camera needs a sealed, dark interior, a smooth aperture, and a shutter that blocks light. Load photographic paper under a suitable safelight, or load film in complete darkness.
• Long exposures need careful timing, and reciprocity failure may call for extra time. Develop paper negatives with the specified chemicals, then scan and invert them; solargraphs use prolonged exposure to record the sun’s path.

How pinhole photography turns a hole into an image

A pinhole camera is a light-tight box with a small aperture on one side. Light passes through the opening and projects an inverted image onto the opposite wall, where photographic paper or film records it.

Why is the image upside down? Light travels in straight lines. Rays from the top of your subject pass through the hole and reach the bottom of the box. Rays from the bottom reach the top. Left and right reverse for the same reason.

This is the camera obscura principle, which existed long before photography. A camera obscura projects an image, and a light-sensitive surface records it.

A smaller hole reduces overlapping rays and improves sharpness, but it also admits less light. If the hole is extremely small, diffraction spreads the light and softens the image. Making the hole smaller forever won’t produce a sharper photograph.

Choose a pinhole size that suits your container

Understand the three common formulas

In pinhole calculations, focal length means the distance between the aperture and the recording surface. There isn’t a lens to focus.

Three familiar formulas estimate pinhole diameter from focal length: Petzval’s 1857 formula, d = sqrt(2 f lambda); Rayleigh’s 1891 formula, d = 2 sqrt(f lambda); and Young’s 1971 formula, d = 1.562 sqrt(f lambda).

Here, d is pinhole diameter, f is focal length, and lambda is light’s wavelength. Use matching units throughout.

For a 50 mm focal length and green light at 0.00055 mm, the formulas give approximately 0.23, 0.33, and 0.26 mm. At this focal length, the largest estimate is about 41 percent larger than the smallest.

Different standards for acceptable sharpness explain the disagreement. A very small hole can soften detail through diffraction. The discussion of Rayleigh’s pinhole calculations shows why the best aperture is a practical estimate, not a universal measurement.

For your first build, choose a pinhole size near Young’s estimate of roughly 0.26 mm.

Calculate the aperture and angle of view

The f-number equals the distance from the pinhole to the recording surface divided by pinhole diameter. A 0.5 mm hole positioned 50 mm from the film gives f/100. The 0.26 mm example gives an f-number of about f/192.

Moving the recording surface closer gives a wider view. With the same pinhole, it also produces a smaller f-number and needs less exposure.

Moving it farther away narrows the view and increases exposure time. Measure the distance rather than assuming every can behaves alike.

Build a homemade pinhole camera

Prepare a dark, light-tight container

For a recycled-can version, use two beverage cans, one 473 ml and one 355 ml. You’ll also need black paint, a sewing needle, electrical tape, fine sandpaper, and photographic paper.

The smaller can becomes the chamber. A section of the larger can forms a removable cap. Cut aluminum has sharp edges, so wear gloves and cover the edges with electrical tape.

Paint or line the interior matte black to reduce internal reflections. Let the paint dry fully before loading paper. Seal unwanted gaps, including the original drinking opening.

A sturdy light-tight box also works. Its flat recording surface makes the distance between the aperture and paper easy to measure.

Make a smooth aperture and shutter

Make a small window in the chamber, then cover it with thin aluminum from the spare can. Pierce the patch gently with the needle tip.

Don’t push the entire needle shaft through. Needle diameter isn’t a reliable guide to pinhole diameter unless you’ve measured it. Keep the pinhole size small.

Sand the patch carefully to remove burrs. The pinhole should be smooth because rough edges scatter light and reduce definition.

Attach the patch securely, then cover the pinhole with an electrical-tape flap. This is your shutter, and it must block light when closed.

Load paper or film without losing the image

Start with photographic paper

A 5 x 7 sheet of photographic paper can be trimmed to fit the chamber. In a can, curve it against the inner wall without covering the aperture.

The chemically treated, usually smoother side should face the pinhole. Load it under a safelight suitable for that paper, never ordinary room lighting.

Keep unused sheets in their sealed black bag. Seal the loaded camera’s lid with electrical tape before taking it outside.

Paper commonly comes in packs of 25 or 100 sheets. Around CA$1 per sheet is a low-cost tutorial estimate, not a guaranteed current retail price. Developing chemicals and scanning equipment cost extra.

Choose film when you’re ready

Paper is convenient for a homemade container, while film gives you conventional negatives. Roll stock requires a transport mechanism; sheet stock needs a suitable holder or dark-loading arrangement.

Load film in complete darkness. A safelight used for paper isn’t automatically safe for it.

Helen Hooker’s pinhole work includes 120 and 4×5 stock, with ILFORD FP4+ and Delta 3200 among her preferred materials. Her Ondu wooden cameras use 0.3 mm pinholes, with configurations around f/160.

Ilford’s starting-out photography FAQs cover the materials and handling behind these first experiments.

Work out an exposure that gives light enough time

Convert a meter reading into pinhole time

Set your meter or metering app to the film’s ISO. For paper, an effective ISO around 3 is a useful experimental starting point, though paper type and daylight spectrum affect sensitivity.

Suppose your meter recommends 1/4 second at f/16. To calculate the exposure time at f/192, multiply that time by (192/16) squared.

That’s 1/4 multiplied by 144, giving 36 seconds before correction. This calculation works with any pair of aperture settings. That gives an exposure of 36 seconds as a starting point.

Modern pinhole exposures commonly range from about five seconds to several hours. Bright sunshine may need only seconds; a dim church can require minutes or hours. Wider pinholes can shorten the time.

For paper, expect tens of seconds or minutes outdoors, with much longer times in dim interiors. A test exposure can help refine your settings.

Allow for reduced sensitivity

During a long exposure, photographic materials may become less efficient at recording light. This effect is called reciprocity failure.

Correction may matter beyond roughly one second for some emulsions or around 30 seconds for some papers. Treat these as broad starting points, not universal thresholds. Each material responds differently, and reciprocity failure may call for extra time.

The Harman pinhole kit instructions explain this loss of sensitivity during long exposures.

Keep the camera stationary and record each exposure time. Try still subjects first. If you want to photograph birds without disturbance, conventional fast-shutter photography is more practical.

An underexposed developed negative usually looks too pale; an overexposed one becomes excessively dark.

Develop and scan your first photograph

After the exposure, close the electrical tape shutter before moving the camera. Return to safe loading conditions before opening it.

For an ordinary paper negative, use photographic paper developer, stop bath or the specified alternative, and fixer. Follow the chemical product’s processing times, then wash and dry the paper. Film requires a separate development process. Follow the instructions for your film and developer.

The exposure is a negative: bright parts of the scene look dark, and dark parts look light.

Scan the dry negative, then invert its tones in editing software such as GIMP. A phone photograph can also work if you use even lighting and keep the phone parallel to the paper.

Correct the orientation after scanning. The projected scene was reversed horizontally and vertically, but the required rotation or mirroring depends on which side you scanned.

Finish with modest contrast adjustments. Pinhole images have their own softness; aggressive sharpening won’t recreate detail the aperture never recorded.

Make a solargraph that records months of sunshine

A solargraph is a pinhole photograph made with a long exposure to record the sun’s path. Each sunny day can leave a curved track, while cloudy periods create gaps.

Use black-and-white photographic paper in a securely mounted, weather-resistant camera. Face the aperture toward the equator, generally south in the Northern Hemisphere and north in the Southern Hemisphere.

Leave the camera in place for at least a month. A longer exposure reveals how the sun’s daily path shifts with the seasons.

Solargraphy differs from ordinary paper-negative photography. The prolonged exposure creates a visible image directly on the paper, which is usually scanned without chemical development.

Retrieve the paper in subdued light and scan it promptly with minimal additional exposure. Pinhole photographers invert and adjust the scan digitally. Unexpected colors can appear even though the original paper was intended for black-and-white printing.

Choose a mounting location where you have permission. A month-long exposure needs a camera that won’t disappear halfway through its astronomical appointment.

Try a pinhole on a digital camera

A DSLR or mirrorless camera can use a pinhole body cap or adapter instead of a lens. Unlike an Ondu film pinhole camera, it records the image on a sensor, so you can skip paper loading and chemical processing.

Choose an adapter that matches the camera mount and blocks stray light. A manufactured pinhole cap is simpler than placing loose homemade parts near the sensor.

Start at a low ISO with the camera supported, then adjust exposure by trial and error. Metering can be unreliable at such a small aperture.

Digital sensors don’t show reciprocity failure. Long exposures can still add noise, and dust may stand out at such small openings.

Frequently Asked Questions

How does a pinhole camera form an image?

Light travels in straight lines through the small opening and projects an image onto the opposite wall of the dark container. Rays cross at the hole, so the image is upside down and reversed left to right.

What pinhole size should I use?

The article recommends starting near Young’s estimate: about 0.26 mm for a 50 mm focal length. A smaller hole admits less light, and an extremely small hole can soften detail through diffraction.

How do I calculate a pinhole exposure?

Multiply the meter’s exposure time by the square of the ratio between the pinhole camera’s f-number and the meter’s f-number. For example, a 1/4-second reading at f/16 becomes 36 seconds at f/192 before any reciprocity correction.

What is a solargraph?

A solargraph is a pinhole photograph made with a long exposure that records the sun’s path over time. Photographic paper usually develops a visible image directly, which can be scanned without chemical development.

A photograph begins with controlled light

You don’t need a conventional camera to record a scene. A dark container, a measured opening, and a light-sensitive surface are enough.

Your first result may be soft or unevenly exposed. Keep the camera steady and change one variable at a time.

Pinhole photography makes the original question tangible: give light a small doorway, and it will draw the view for you.