Pinhole Cameras vs Cyanotype: Two Ways to Skip the Lens

Someone has already run the experiment. A bucket pinhole camera with a hole giving roughly f/295 — the kind of camera that exposes ordinary darkroom paper in one to five minutes — was loaded with cyanotype-coated paper instead and aimed at a garden. After eight hours there was not the slightest imprint on the sheet. A fresh paper left in for five weeks of Scandinavian summer, with sun for most of the day and most of the night, came out with a few faint streaks. Six months produced a slight blue patch in one corner and nothing else.

That failure is the fastest way into the comparison. Both processes work without a lens, and the shared trait makes them sound like two settings on the same idea. They are not. A pinhole camera is a camera with the glass taken out: it still projects a scene from across a room or across a valley onto whatever sits at the back. A cyanotype has no optics and no projection at all — it records only what is physically pressed against its surface. Swapping one light-sensitive material for the other does not give you a slower version of the same photograph. It gives you a blank sheet, because the two processes answer different questions.

A pinhole has an f-number exactly like a lens, set by geometry instead of glass: divide the distance from the hole to the film by the diameter of the hole. Built cameras land somewhere between about f/70 and f/560, which is why exposures run from a fraction of a second to hours. The hole does a lens's job badly on purpose. Nothing focuses, so a few centimetres away and the horizon are rendered at the same modest level of detail — depth of field is close to infinite, and sharpness is not for sale at any price.

Inside the camera goes either film or ordinary darkroom enlarging paper. Paper is the cheaper route and the one most beginner pinhole setups are built around, but it is slow, commonly rated somewhere between ISO 3 and 6. It also has almost no exposure latitude: paper spends nearly its whole range producing the image, with none of the cushion film gives you for a bad guess. Either material leaves the camera carrying a latent image that is completely invisible until it goes through chemistry, and the picture it holds is a negative.

A cyanotype begins as two iron salts — ammonium iron(III) citrate and potassium ferricyanide — mixed in equal parts and brushed onto paper or cloth. Ultraviolet light converts the coated areas into Prussian blue, an insoluble pigment that forms among the paper fibres, and everything the light never reached stays water-soluble and simply rinses out. That rinse is the whole development step: cold water for at least five minutes, ten if you have the patience, until it runs clear. No developer, no stop bath, no fixer. Because the coating responds to ultraviolet rather than visible light, you can mix the solution in normal room light, coat in a dimly lit room away from windows, and dry the sheet in the dark.

What the paper cannot do is see. With no optics involved, a cyanotype is a contact print, and the defining property of a contact print is that it comes out the same size as the thing that made it, rather than being projected through an enlarger. Lay ferns, lace or feathers straight onto the dry coating and you get their silhouettes in white. Lay a film negative on it and you get a tonal photograph, in blue. Either way the image arrives while you watch: the highlights turn green, the mid-tones go blue, and the shadows reverse to a pale grey-blue that looks badly overexposed — that reversal is the cue to stop. Nothing about what a cyanotype actually is requires a camera at any stage.

Cyanotype reaches a finished object sooner, and the reason is logistics rather than skill. Everything it needs is a dim corner, a brush, a sheet of glass, sunshine and a tap, and the only real wait is letting the coated sheet dry — an hour to a day, depending on temperature and humidity. A pinhole camera is trivial to build and genuinely cheap, but the picture stays locked inside it until you have a room you can black out, a red safelight and three trays of chemistry — and that is the step most people stall on, not the camera.

Pinhole earns its place if what you want is photographs of things: a street, a building, a long exposure of a moving sky. No contact process can ever do that, because nothing is in contact with the paper. If even coating a sheet sounds like one step too many, photograms and lumen prints make contact images on photographic paper straight out of the packet, which is the shortest route to a physical image of any of these.

The workable combination runs one way only. Use the pinhole camera for the thing it does well — projecting a scene — and let the cyanotype do what it does well, which is turning a negative into a permanent print with no enlarger involved. Shoot the negative on film, or shoot a paper negative, scan it and output a digital negative onto transparency film at the size you want the print. Then sandwich negative against coated paper under glass and set it in the sun. Practitioners who tried the in-camera route and failed arrive at exactly this conclusion: make the negative with the pinhole camera, then print the cyanotype from it.

Plan around the size ceiling, since contact printing cannot enlarge: the negative's dimensions are the print's dimensions. And if making the cyanotype inside a camera remains the goal despite all of the above, the people who manage it drop the pinhole for a lens — a magnifying glass at its widest aperture with a short focal length — and switch to the faster modern cyanotype formula, which brings each frame down to roughly forty-five minutes to an hour instead of months. The older formula is too slow for that job and the image tends to wash away during development. The coating and contact-printing half of this workflow is the same one a beginner cyanotype setup is built for.