Pinhole photography

How the opening works

A pinhole camera needs no glass lens; the image forms when light passes through a small opening and spreads onto film or photographic paper. The simplicity is useful, but the opening has to be small enough to keep the image crisp and large enough to admit light. For a camera with a 25-millimeter distance from hole to material, a hole near 0.2 millimeter across is a sensible starting point. That gives roughly f/125. The result is less a miniature lens than a controlled opening — simple, but sensitive to small errors.

[sdm_callout type=”tip”]Last checked by the editors in 2025.[/sdm_callout]

That distance, often called the focal length, also affects framing. A 25-millimeter camera sees a wide area, so a nearby tree or cup can fill much of the picture while distant buildings stay small. There is usually no viewfinder to show exact edges. Before exposing anything, point the camera at a few scenes and note how much of each one fits. A cardboard rectangle held at arm’s length can serve as a rough guide. Keep the sun out of the opening unless you want a pale flare across the image.

Build a steady body

A clean metal tin or a small cardboard box makes a workable body. Paint the inside matte black, or line it with black paper, to reduce reflections. Make the hole in thin foil rather than in the thicker wall: press a fine needle through gently, then smooth the foil flat and inspect the opening against a bright window. A round, burr-free hole matters more than a perfectly precise measurement. Tape the foil over a larger opening in the body, and cover every seam that could admit stray light.

The photographic material must sit flat opposite the hole, with its sensitive side facing inward. A small curved back can help keep paper from lifting at the edges. For roll film, check that the film leader lies flat as it passes the gate and that the spool turns without tugging; a crooked strip may partly cover the image area. Make the camera easy to open and close in dim surroundings, and mark the hole’s position on the outside so you can aim it without touching the foil.

Set exposure by testing

Pinhole exposures are often measured in seconds rather than fractions of a second. A phone light meter can give a starting estimate if you enter the camera’s approximate f-number, but treat the result as a guess. If it suggests one second, make a first exposure of one second and another of two or four seconds. A hand covering the opening can act as a simple shutter; lift it cleanly, keep your hand clear of the hole, then cover it again. A small clamp or a hinged flap can be more repeatable.

For a route with just a few planned subjects, shooting a single roll keeps the tests manageable and makes it easier to compare frames. Write down the scene, the estimated time, and the actual exposure beside each frame number. If you are pushing Tri-X by one stop, mention that clearly when you send the roll for processing, since the change affects both exposure and the way it is treated afterward. For paper, start with a brief test strip of exposures; bright midday scenes may need seconds, while shade can take considerably longer.

Read the finished print

A pinhole image usually has softer detail toward the edges, generous depth of field, and a slightly dreamlike perspective. Small subjects can look unexpectedly sharp when the camera is steady. If every frame is pale, shorten the exposure or make the opening smaller; if everything is dense, give less time. Change only one variable between tests. A tripod or a bag set on a wall helps prevent the whole scene from smearing. With paper negatives, reversing tones for a positive print takes another step, so keep the original test notes with the sheets.

Expect some unevenness. A hole that is oval or ragged can soften one direction more than another, and a loose back may shift the paper during exposure. Look closely at a few results before remaking the camera. A small label with the date and camera dimensions can be useful if you display a print; the photo credit line might read, “Pinhole photograph made with a 25-millimeter camera.” The first result may be blank or too dark… that is still useful information. Adjust the timing, check the hole once more, and try the same scene again.