The Large Pyramid at Coba, Mexico – pinhole camera photograph 2002 17 minute exposure
Pinhole Camera Basics: What is a pinhole camera and how does it work?
The pinhole camera is based on Leonardo da Vinci’ s invention of the Camera Obscura, Latin for “darkened room”. That was a completely dark room with a tiny hole in one wall that admitted light. An image from the outside world is projected directly across from the hole. It appeared upside down on a piece of paper for tracing. The Camera Obscura evolved in the 18th Century into a device used by artists to understand and trace linear perspective.
My pinhole camera is a small wooden light tight box that has a very tiny (.020” or 5mm) hole in a metal shim. This is the pinhole camera’s aperture. It projects light onto the film that is secured on the back in a film holder. The film for this camera is 4” x 5”, so it makes a big negative. I have an Epson Perfection V700 scanner with a transparency head. With it I can scan the negatives and print with no darkroom.
For now I have left the photographic purist behind out of necessity by not printing the images photographically. From 1992 until 2002 I printed in B&W and alternative printing processes including Kallitype, Cyanotype, Van Dyke Brown, and Platinum/Palladium. I plan to start making Cyanotype prints (which create deep blue images), again soon
Jump ahead 600 years to the pinhole camera.
My 4×5” pinhole camera with a filmholder inserted, ready to shoot
About Exposure
We are working with a tiny aperture, so very little light can enter the camera. As a result, long exposures are necessary. This pinhole is a fixed aperture. Hence, there is no way to adjust it’s size to let in more light. The only control I have over exposure is the length of time that the simple shutter is open.
Normal shutter speeds for modern cameras range from 1 second to 1/4000th of a second. Apertures are quite large on most digital SLR cameras compared to the pinhole. The exposures for the pinhole range from 1 second to several hours depending on lighting conditions. A sturdy tripod is a necessity for holding the camera steady during long exposures. A light meter is also needed.
The light meter tells me what a normal exposure is. But the normal reading beyond 1 second requires adjustment for a proper exposure. A thing called reciprocity failure happens with long exposures. This is because the film becomes less sensitive with exposures longer than 1 minute. Strangely, you solve this by increasing the exposure even longer.
To solve this issue, increase the meter reading’s exposure time. I do this by raising it to the power of the reciprocity factor of your film. For my film the reciprocity factor is 1.26. One can do the math, but I use an online calculator. So, a 15 second exposure becomes 30 seconds, and 15 minutes becomes 1 hour and 30 minutes.
Film Processing
I was fortunate to have a darkroom off and on from 1995 until 2005. When I made a move that year, I lost the space to work. Since then, I have made some changes. In 2005 I began working with the pinhole camera using color transparency film. This gave me a positive color image on film. This had to be commercially processed. That continued in a limited fashion, and I got great results, but it was too expensive to continue. The color transparency films have gotten both scarce and expensive today, making it a distant choice.
Not having a dark room, and not having access to color film. I’ve had to find a solution for developing my own film. I have done this by purchasing a Stearman 645 developing tank. While not an ideal solution, it functions quite well for my needs.
