Pinhole photography borrows its vocabulary from ancient optics and from the analogue darkroom, and a few words keep coming up as soon as you get started. This page defines them simply, in the order you come across them in practice, and points to the article that covers each notion in detail, the same notions our guide links together across the complete journey of a pinhole photograph, from the box to the print.
The vocabulary of pinhole and analogue photography
Pinhole camera (sténopé)
A camera reduced to the essentials: a black box with a tiny hole that replaces the lens. The French word sténopé comes from the Greek stenos (narrow) and ope (hole), literally a narrow hole, and in English it is called a pinhole, the hole made by a pin. It is also the name of the hole itself.
Its advantages come from this simplicity: no focusing, almost total depth of field and a soft rendering.
Camera obscura
The ancestor of the pinhole camera, a dark room or box in which a small hole projects the inverted image of the outside world onto the opposite wall. The principle has been known since Antiquity and records nothing by itself: it only forms the image, which you observe or trace by hand.
Dark chamber and darkroom
In French, the same term, chambre noire, means two things. Inside the camera, it is the dark space where the image forms. In analogue photography, it is also the room where photos are developed away from daylight: the darkroom.
Shutter
What opens and closes the way in for light. On a pinhole camera there is nothing mechanical about it: it is most often a flap or a piece of card that you move away from the hole to start the exposure and put back to end it.
Focal length
On a pinhole camera, the distance between the hole and the paper, in other words the depth of the box. It determines the angle of view, a short box framing wide and a long box framing tight, and it also governs the ideal diameter of the hole.
Pinhole diameter
The size of the opening, in the order of a few tenths of a millimetre. The right diameter is worked out from the focal length rather than from a single figure. The pinhole calculator gives you the right diameter for your focal length.
Diffraction
The phenomenon whereby light spreads out when it passes through a very narrow opening. It is what prevents you from shrinking the hole indefinitely to gain sharpness, and it sets a lower limit on the diameter.
Depth of field
The extent of the scene that appears sharp, from the foreground to the far distance. Because the hole is tiny, a pinhole camera offers almost total depth of field: everything is more or less sharp at the same time, without any focusing.
Photographic paper
The surface that records the image. When starting out, you slip a sheet of black and white photo paper into the box, without film, because this paper can be handled and developed under a red lamp. To try it for yourself, the Sténoflex contains everything you need, from taking the picture to developing it.
ASA and sensitivity
The measure of how strongly a surface reacts to light, expressed in ASA (or ISO). The higher it is, the shorter the exposure. Photo paper has very low sensitivity, around 3 to 6 ISO, which explains the long exposure times of pinhole photography.
Exposure time
How long you let the light in, from a few seconds in full sun to several minutes, or even hours, in low light. With no mechanism, you estimate it and adjust it.
Latent image
The invisible image recorded in the paper or film after the exposure, before any developing. It already exists, fixed in the sensitive material, but nothing appears until a chemical bath brings it out.
Developer
The first developing bath, which brings out the latent image by darkening the areas that received light. This is the step where the image gradually emerges before your eyes, under the red lamp.
Stop bath
The intermediate bath, often water or a mild acid, which instantly stops the action of the developer so that it does not go too far. It also protects the next bath by preventing the developer from contaminating it.
Fixer
The last chemical bath, which makes the image stable and insensitive to light by removing the unexposed sensitive material. Once fixed and rinsed, the photo can be taken out into daylight without worry.
Safelight
A light to which the sensitive surface reacts very little, in practice the red lamp of the darkroom. Since black and white paper is not very sensitive to it, you can load the box, develop and watch the image appear without fogging it, as long as you keep the lamp at a good distance.
Negative
The image you get first, in which the tones are reversed, light becoming dark and vice versa. With a pinhole camera on paper, you end up with a paper negative, which you scan and then invert, or contact print to obtain a positive.
The vocabulary of cyanotype
Cyanotype
A photographic process developed by John Herschel in 1842. Iron salts spread on the paper react to ultraviolet light and, after a simple rinse in water, give a deep blue image.
Prussian blue
The pigment that forms the cyanotype image. Stable over time, it can fade under prolonged exposure to light and then partly regenerate in the dark, and it is sensitive to alkaline conditions.
Ferric ammonium citrate
The light-sensitive iron salt. Under ultraviolet light, its iron changes from the ferric state to the ferrous state, which starts the formation of the blue.
Potassium ferricyanide
The second salt in the mixture, which combines with the reduced iron to form Prussian blue. Potassium ferricyanide has low toxicity at the amounts used in the process, but it can release cyanide on contact with an acid, or under UV light when in solution: it must never be brought into contact with an acid.
Sensitising
Spreading the mixture of equal parts of the two solutions on the paper, then leaving it to dry in dim light. The paper then becomes sensitive to ultraviolet light.
UV exposure
Exposing the sensitised paper to ultraviolet light, in the sun or under a lamp. It lasts from a few minutes in high summer to much longer under an overcast sky or in winter.
Photogram
A photogram is an image made without a camera, by placing objects or plants directly on the sensitive paper. The shapes shielded from the light stay white on a blue background.
Toning
A bath applied after rinsing, with tea, coffee or other tannins, which shifts the colour of the print towards brown, purple or black.
Éric Marais — Photographer, author of two books on pinhole photography (published by Pearson) and creator of the Sténoflex. He has run introductory workshops in pinhole photography and analogue developing from the very beginning.