The Pinhole Camera – The Origins and How to Build One
Enter into a dark room and make a small round hole in the window shade that looks out onto a bright outside scene. Hold a piece of translucent paper 6–12 inches from the hole and you will see what is outside. This optical phenomenon, which dates back to the ancient Greeks, provides the basis for making pinhole (camera) photographs. Note that the image will be upside down, the same as in our eyes – our brain turns it right side up.
Birth of the Camera
This optical observation lead to the invention of the camera obscura (Latin for “dark room ”), which is a drawing device used to project an image onto a flat surface where it can be traced. By the sixteenth century the camera obscura was in common use by artists, such as Leonardo da Vinci. In 1658 Daniello Barbaro placed a lens on the camera obscura. It was this device that helped to work out the understandings and uses of perspective, which had been baffling artists, scientists, and scholars for centuries. Daguerre’s camera was an uncomplicated camera obscura with a lens.
How the Camera Works: Circles of Confusion
An optical image is made up by what is known as tiny circles of confusion. Technically, the circle of confusion is the size of the largest circle with an open center, which the eye cannot distinguish from a dot, a circle with a filled-in center. It is the major factor that determines the sharpness of an image and the limiting factor of depth of field. When these circles are small enough to form an image they are called “points ” and the image is considered to be in focus. The pinhole camera has infinite or universal depth of field, because it creates circles of confusion that are about the same size as the pinhole all over the inside of the camera. These tiny circles of confusion are small enough to be considered points of focus that have enough resolution to form a coherent image. This means that everything from the foreground to the background appears to have the same degree of sharpness. This uniformly soft, impressionistic image is characteristic of pinhole photographs. Adding a lens makes smaller points of focus and thus creates a much sharper and more detailed, coherent image.
Building a Pinhole Camera
For a couple of dollars and a few hours of time, you can build a simple pinhole camera. Many photographers find it gratifying to use their hands to build a camera that in turn forms the basis of their photographic vision. The pinhole camera removes you from the expensive high-tech environment of the standard formats of automatic cameras and returns you to the basic function of vision.
You can make a pinhole camera out of any structurally sound light-tight container (avoid shoe boxes). A 4 x 5 inch film box (100 sheet size) makes a good first pinhole camera with a wide angle of view, because the closer the light-sensitive material is to the pinhole, the wider the field of view and the shorter the exposure. Oatmeal boxes and coffee cans are also commonly used. One can also be built from scratch.
Pinhole Camera Building Materials:
1. Sheet of stiff matt board or illustration board at least 1/16 inch thick. One side of the board should be black. This will be the inside of the camera. The black helps to reduce internal reflection.
2. Sharp X-Acto (number 11 blade is good) or mat knife.
3. A 2 x 2 inch piece of brass shim or aluminum. An offset plate, obtained from a printer, is ideal. You can also use an aluminum pie pan or TV dinner tray.
4. Glue. Any household white or clear glue is fine.
5. Steel-edged or plain straight-edged ruler will deliver a far more accurate and close cut than a cheap plastic or wooden ruler.
6. #10 or #12 sewing needle.
7. Small fine file or number 0000 sandpaper.
8. Ballpoint pen.
9. Black photographic pressure tape or black electrician’s tape.
Making the Pinhole:
Get a thin (0.002) piece of brass or aluminum about 2 inches square from an automotive or hardware store. Also obtain a sharp, unused sewing needle. A #13 needle is ideal for a 4 x 5 inch film box (the smaller the pinhole, the sharper the image and the longer the exposure time). Since the distance between the front and back of the box is short, a larger needle hole could result in exposure times that are too short.
Hold the needle between your thumb and index finger and gently drill a hole in one side of the metal. Then turn the metal over and drill the other side. Do not stab a hole into the metal. Use very fine sandpaper to remove any burrs around the hole. Repeat this procedure until the opening is the same size as the diameter of the needle. By drilling, sanding, and slowly expanding the hole, you should end up with an almost perfectly round aperture without any burrs. The more perfectly round and burr-free the pinhole, the sharper the image will be.
After completing the drilling operation, find the center of the front of the camera box. At this center point, cut a square opening equal to half the diameter of the metal pinhole material (1 inch square). Save this cutout for use as a shutter. Center the pinhole metal inside the box and secure it with black tape.
Darken the cutout on all sides with a black marker. If necessary, put black tape around the sides so it fits snugly back into the camera front, over the pinhole. Let a piece of tape stick out to act as a tab-type handle. This handle will allow the cutout to form a trapdoor-style shutter that can be removed and replaced to control the exposure time. Another option is to simply use the black plastic top from a film container and hold it in place with your hand or tape. Aluminum foil and tape also work.
The Aperture Formula:
To determine the f-stop of your pinhole camera, simply measure the distance from the pinhole to the film plane and divide by the diameter of the pinhole. The formula for calculating the f-stop is: f= v/d where f equals aperture, v equals distance from pinhole to film or paper, and d equals pinhole diameter. For example, a 0.018 inch pinhole at a distance of 2 inches from the paper (focal length) produces an f-stop of 111.
Starting Paper Exposure Times:
Begin by exposing black-and-white photographic enlarging paper outside in daylight. Single-weight fiber paper without any printing on the back works best. This paper is readily available, inexpensive, easy to process, and you can see exactly what is happening under the safe light. Typical daylight exposures with a film-box camera can run from 1 to 15 seconds, depending on the time of day, the season, the size of the pinhole, and the focal length (the distance from the pinhole to the paper).
After making the exposure, process the paper using normal black-and-white methods. If the paper negative is too dark, give it less exposure time. If it is too light, give it more exposure time. Trial and error should establish a paper negative with proper density within three exposures. When you get a good negative, dry it and then contact print it (emulsion to emulsion) with a piece of unexposed paper. Light will penetrate the paper negative. Process and then evaluate the paper positive. Make exposure adjustments and reprint until you are satisfied. After experience is gained it is possible to expose any type of photographic material in the pinhole camera.
After you have mastered the camera and the black-and-white enlarging paper, you are ready to expose any type of photographic material in the pinhole camera. Materials may include black-and-white or color film, regular RA-4 color paper, Ilfochrome (which gives a direct positive), and even Polaroid materials such as SX-70, which can be processed in an SX-70 camera.
Converting a 35 mm Camera to a Pinhole Camera
You can convert a 35 mm camera to a pinhole camera by covering a UV filter with opaque paper in the center of which you have made a good pinhole. Attach the pinhole filter to the camera’s lens and it becomes a pinhole camera. You also can convert an old snapshot-type or disposable camera to a pinhole camera by removing its lens and replacing it with a pinhole aperture. Zero Image Company (www. zeroimage.com) makes a modified body cap, called a Zone Plate, for various film and digital cameras that has a laser-cut pinhole. They also make wooden pinhole cameras.
Since first appearing in 1990, Photographic Possibilities has become a concise and trusted resource for individuals desiring to actively interact with the photographic process in order to thoughtfully interject their personal responses to the subject being portrayed. The book presents a stimulating survey of works by over 150 contemporary international photographers that illuminate, not illustrate, concepts, and methods discussed in the book. Each reproduction is accompanied by a caption in which the artist explains the ideas and the techniques that went into making the image.
Excerpt from Photographic Possibilities: The Expressive Use of Equipment, Ideas, Materials, and Processes, 3rd Edition by Robert Hirsch © 2008 Taylor & Francis Group. All Rights Reserved.