Pinhole photography
The pinhole camera is the oldest form of camera in photography. Indeed the pinhole camera in the form of the camera obscura predates the image fixing of photographs by hundreds of years. Artists drew from images formed by pinholes for accurate perspective. Natural images formed by pinholes or small apertures have always existed formed by gaps between leaves or cracks in rocks. Images of the sun can often be seen. The telltale sign is a circular image of the sun (often 1ft or more across when the sun is low). This is formed even when the aperture is not circular. Pinhole cameras are capable of producing high quality images when constructed with care. The Pinhole camera has different qualities to conventional lens photography, which need to be taken into account when taking photographs. The image is formed by a very small aperture compared to an image formed by a lens. The exposures need to be long- from seconds to hours. Motion is blurred or invisible. Another feature is the lack of depth of field produced by lens photography, all objects appear equally sharp from the nearest point to infinity. Both of these qualities allow unconventional images to be produced. The photographs produced are about a period of time rather than the near instant we have become used to.
The plus side of this is that the cameras can be produced very cheaply and easily from all sorts of items. Boxes and metal cans are the first choice but more exotic image may be produced from oddly shaped items, shells, cardboard rolls, and even whole rooms! Conventional cameras can also be adapted to allow more than one shot per session. SLR cameras are easily usable as the lens can be replaced by extension tubes or cardboard and a pinhole. This gives the added advantage of a 36-exposure film and conventional processing.
One particularly easy method is to us to aluminium drinks cans. Two cans are cut and shaped as shown. Smooth down or tape the cut edges. The inside must be painted matt black (try a spray, two coats). A piece is cut from another can (1 inch square) for the pinhole.

See Diagram.

If you wish to calculate the size of the pinhole for your self use the following formula-

pA=sq. root of 55f

Where pA= aperture in thousandths of a inch
F= Focal length in inches

To find the effective aperture for the pinhole, divide the focal length by the pinhole diameter.
If you not choose to work it out, try using a needle (see below) to make a hole and smooth down both sides with very fine emery paper to reduce any burring. The edges of the hole need to be as clean as possible. Some experimentation may be needed to produce the sharpest image. Suggested sizes given below the drinks can camera.

For 55mm the pinhole required is approx. 0.27mm or 0.01 inches diameter. This is obtained by using a number 15 needle.

aperture =55/0.27
=203.7 approximately f204.

When complete the camera requires a black piece if insulating tape over the pinhole as a shutter. The camera can then be loaded in a darkroom or changing bag with a small piece of paper or film stuck to the back with Blu-tak (emulsion towards the pinhole). It is a good idea to load several at a time.

Other useful sizes are-

Focal length pinhole diameter f-stop
Inches mm
50 0.0103 0.261 191
100 0.0146 0.370 270
150 0.0178 0.453 331
200 0.0206 0.523 382
250 0.0230 0585 427
300 0.0252 0.641 468
350 0.0273 0.692 506
500 0.0333 0.827 604

Exposure Exposure is a problem at first but with care good results can soon be produced. Think carefully about exposures As the light from the image falls off with the inverse square law, doubling the focal length requires 4x the time. In fact it will require more due to reciprocity failure, often much more as the exposure becomes many minutes.
By recording results, good exposures for a particular camera can soon be made. Photographic paper can be used and is best for first trials. The resulting negative can then be contact printed for a positive print. Monochrome and colour negative and positive materials can also be used for better results once exposure is sorted out. However sheet film materials are expensive so adapting a 35mm or 120 camera may be a cheaper option, allowing many cheap exposures.

Here are some suggested exposure times for the drinks can camera-

For 100 ISO film or paper.
1 min. bright sunshine.
2.5 cloudy bright.
3-4 min. dull.
5 min. indoors-bright room.

Try to work in stops- Doubling or halving exposure. If your negative is very underexposed (lacking in density) an increase of 10 seconds on a ten minute exposure will not make a difference. Try 20 min. or 15/17 min. for a more practical increase in exposure.

Tips for pinhole photography.

Record your exposures-try resin coated paper (assuming access to a darkroom) at first as this allows quick trials and the negative can be contact printed. Try not to have a bright light-source in the view as this tends to cause flare and low contrast.
Mount the camera solidly on a tripod or stand on a firm surface.
Try to work out the angle of view with the first few exposures. Perhaps make a simple viewfinder?
Subjects with a wide tonal range are good but try to avoid extremely bright highlights.
Close ups are often very effective.

Why not send me your best efforts?

Recommend reading- Pinhole Photography-rediscovering a historic technique By Eric Renner. Focal press. Pinhole photography in impressive depth with interesting historical information.

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