Back to Basics

All cameras, from the most sophisticated to the pinhole, rely on the same elementary principles, performing in similar fashion to the human eye.Like your eyes, the camera needs light to operate. Light moves into the eye through the pupil, a hole that is made smaller or larger by the iris.

Light gets into the camera through a hole called an aperture that is made larger or smaller by a diaphragm. The camera can also shut out all light with a shutter, similar to closing your eyelids, or opening them to let the light pass.

Recall what happens when you enter a movie theater on a sunny afternoon. It takes some time for your eyes to adjust to the low light. At first you cannot see anything, but soon you began to make out objects and within a short time you can see pretty well, even in that darkened room.

This is much like a camera making a long exposure in low light. The diaphragm opens as wide as it can to allow maximum illumination. For your eyes, the iris opens wide. The eye's retina, like the camera's film, is sensitive to changes in light and sends messages to the brain about the images you see. As you leave the theater and return to the sunlight, the opposite situation occurs. The eye's iris closes down as it's flooded with light. In bright light the camera's diaphragm closes down, or stops down.

Unlike the camera, the eye is constantly and automatically reacting to various fight and focusing and refocusing. The camera has to be adjusted for each situation. The camera, however, can bring into focus objects both near and far and record them on film at the same time. Your eye cannot.

While modern cameras and the human eye use sophisticated systems to focus images, including color correction and lenses to improve clarity and magnification, much simpler techniques can and do work.

Consequently, the pinhole camera can produce surprising results using just a light-tight box to capture the image transmitted to film through a simple hole (aperture) made with a pin or, for a better level of performance, a sewing needle .

Constructing the camera

Keep in mind that a sturdy container usually has better light keeping properties, is easier to work with and will last longer. The best overall size is in the neighborhood of six inches square. The shape of the box can present some real creative possibilities and the box depth, from removable cover to back, relates to the angle of view of the transmitted image. In other words: a container that is very shallow will yield a wide angle view; and a container with depth will yield a telephoto image.

For purpose of explanation, let's assume that a sturdy, cardboard box about six inches square and four inches deep is used for the camera body. The bottom of the box will be used to hold the film (more on that later) and the box top or lid will become the light-transport system (aperture, shutter). Some would choose to line the box with black paper or paint it black to cut down on the possibility of stray light, but it the lid is properly prepared, or if the lid is equally as large as the box itself, that won't be necessary.

To convert the lid to an aperture you will need to first cut out a hole in the center of the lid about one-inch square. Cover the hole with as heavy a grade of aluminum foil as you can find and tape it down with black plastic electrician's tape. Then using a small sewing needle, carefully punch a hole in the center of the foil with the needle, taking care not to move the needle from side-to-side. An easy, but deliberate, straight-in-straight-out, motion will work nicely.

The foil will provide a much more accurate aperture unlike one made by punching the needle directly through the lid. Also, it gives you the opportunity to repeat the process if need be with the minimum of trouble. It may also be easier to punch the hole in the foil prior to taping it on the camera. Greater accuracy can be obtained by using a cushion underneath, like a phone book or piece of cardboard.

A more sophisticated aperture can be made by using thin, brass shims which can be found at a good automotive supply or hardware store. The difference of making an aperture in cardboard, aluminum foil or brass shims can be noticed in the clarity and sharpness of the final photograph. Modern cameras use computer designed lenses, ranging from hand ground glass to machine ground plastic. But the aperture itself can function as a lens.

The pinhole (in this case, needle hole) transmits rays of light so that they strike the film in tight clusters. The result is an acceptably clear photo. Results are improved with better materials, but also with smaller apertures. Size makes a difference because the smaller aperture transmits only a few rays from each point reflected from the scene. The finer the rays of light, the tighter the cluster hitting the film and the better the representation of the image viewed In other words, pin-point accuracy.Larger apertures will transmit a much softer and less focused image. Experimenting with the foil apertures of various sizes will provide a dramatic illustration.

Shadow catching

Photographic film is made in layers.The base is clear plastic coated with light sensitive material held in place by an emulsion layer. The light sensitive material is actually tiny particles of silver that when exposed to light, chemically react and etch a reflection of the image viewed. Not all film reacts the same. Some, with larger silver particles, is more fight sensitive and color film is different than black and white, either having more layers to capture various hues or using dyes. All film, and photographic papers, have an emulsion layer. This is actually a gelatin that holds the silver in place. The emulsion is fastened with adhesive to the plastic film base and then coated with a scratch resistant material.

Two additional pieces of photo trivia will aid in the understanding of the photographic process related to the transmission of light and film:

1. The image viewed by the camera is recorded upside down on the film. Our eye functions identically, but the brain reverses the image. Modern cameras have a system of mirrors that reverse the image as you look directly through the lens.
   
2. The scene is recorded on the film as a negative image. In other words, whites are black, blacks are white, etc. That means then, that the white parts of the negative image are actually unexposed silver particles and the black parts are fully exposed.

Suggested exposure times
   outside, bright sun: one minute
       outside, cloudy: five minutes
  inside, sunny window: eight minutes
    inside, sunny room: 14 minutes
     inside, dim light: 30 to 40 minutes

Returning to the darkroom with your exposed negative you will unload the camera -- again under safelight conditions -- and process the print in a series of chemical baths. Each chemical should be pre-mixed and placed in plastic trays commonly used for the purpose. All of the following materials are readily available at any decent camera supply store.

The first processing solution is the paper developer. Dektol, a Kodak product is common. Developer can be mixed 1:2 (one cup Dektol, two cups water) and it will turn brown when exhausted. Under the safelight, gently slide the photo paper negative into the solution and rock the tray carefully. It is a good idea to use photo tongs (not metal tongs) to handle the print. Some people may react to the developer using their hands and there is also less chance of chemical contamination from tray to tray. Each tray, other than the water baths, should have separate tongs. The negative image will begin to appear after a few seconds in the developer. After about two minutes, development has been achieved and the negative, if properly exposed, will not change. If the negative has been severely overexposed it will turn completely black.

From the developer, the negative is placed in a water bath that removes the Dektol and arrests development. The negative is then placed in the fixing agent. Kodak fix, or fixer, is a chemical that removes all the unexposed silver particles and hardens the paper surface. After a few seconds in the fixer, room lights may be turned on. Total time in the fixer need not exceed four minutes. The negative is then placed in the last water bath for about four minutes.

(Once the room lights are on you will notice, for sure, if you have exposure problems and need to try again. You will also notice how sharp the image is and exactly what a negative image looks like. It will take some experience to judge the quality of a negative. If you have had success so far, then the most difficult parts are now behind. All that's left is reversing the negative to a positive print.)

If this is your first darkroom experience then you will want to see a "real" print as soon as possible. Fortunately, with pinhole photography you won't have to wait long. You can even process a print before the negative dries. In fact, often it is easier that way. What you need is another piece of photo paper the same size as your negative or slightly larger.

Remember to turn off the white light and handle the paper only under a photo light! If your darkroom has an enlarger -- machine for printing prints from negatives -- you can use its light source for the printing process. Turn on the enlarger --keep photo paper packaged-- and adjust the size and shape of the light it projects so that it is several times larger than your intended print. Place a photo easel under the light, or mark the top edge of the light beam with tape, and turn the enlarger off.

Now, with all the lights off, except the photo light, remove a sheet of fresh photo paper and place it emulsion side up in the easel, or where the light will strike, marked by the tape. Place your negative, wet or dry, upside down and directly on top of the photo paper. If the negative is wet, roll out any bubbles with your hand or a roller made for that purpose. If the negative is dry you will probably have to sandwich it and the photo paper under a clean and rather heavy piece of glass. You are now ready to make a second exposure. This time exposing the paper to the enlarger's light that will pass right through the negative and reverse the image on the photo paper by creating another silver particle reaction.

Now, run the newly exposed piece of photo paper through the same chemical process and, there you have it, a wet, but finished black and white positive print. Blot off the excess water, or use a photo squeegee and set it out to dry. The resin coated paper will dry soon and dry flat. If you are in a big hurry for a final dry print, use a hair dryer, taking care not to crackle the resin coating with heat too high. Some photographers have been known to use a microwave to dry resin coated prints.

If you do not have an enlarger, or access to one, you can still make a positive print. Just turn on the room light. This will take some experimentation as the light won't be as concentrated as under the enlarger's lamp, but will work.

Additional Help

Renner, Eric. Pinhole Photography, TR268 .R46 1995

Oakes, John Warren. Minimal Aperture Photo, TR268 .024 1986

Smith, Lauren. Visionary Pinhole, TR268 .S65 1985

Smith, Lauren. Pinhole Vision I, TR268 .S64x 1981

Smith, Lauren. Pinhole vision II, TR268 .S642x 1981

Eastman Kodak. How to make..., TR268 .E38x 1976