About a year ago I started building pinhole cameras, experimenting with old cigar boxes.
My first camera is designed to accept a roll-film back made for Graflex-type cameras. That's still a work in progress, as I'm having trouble with the film back not working properly. More on that as it develops...
The next project I tackled (shown here) was with a different style cigar box. This one has a 55mm focal length and instead of using film, it takes photo paper about 5 x 7 inches in size. I drilled a 1-inch hole in the middle of the top of the box. The aperture is made with a thin piece of copper and has a diameter of .0135 inches. I made the hole with the smallest micro drill I had. I know that it should be a little smaller than that for the focal length, but it's a baseline for me to work from.
The shutter is cut from a piece of plastic, actually an old mud flap for a car, fastened with a simple machine screw and nut. Inside the camera, I put two slightly raised strips of plastic at each end of the bottom so the paper could be inserted under the lip to hold it in place.
Why I decided to test it on one of the colder days of winter I have no idea. I have an old changing bag I purchased at an estate sale so I could make multiple exposures in the field. I wasn't very picky about the location. I just wanted a good place to work. In this case I had an iron railing to brace the box against, and a bench to set the changing bag on.
So I would load a piece of paper in the bag, take it out of the bag, make the exposure, put it back in the bag, close it, take out the paper and put in a new sheet, repeat. Unfortunately, the paper I cut wasn't uniform so it wasn't always a tight fit.
I made exposures of 2, 4, 8, 16, 32 and 64 seconds as a test. By the third exposure my fingers were so cold I couldn't feel which was the light-sensitive side of the paper. But I guessed correctly since they were all arranged facing the same way.
Back home, I set up a makeshift darkroom and processed the paper. It turned out that 2 to 4 seconds was about right for this overcast day. I expected it to be longer, but then again I had no idea of the real exposure value of the paper.
I picked the most properly exposed negative and made a contact print while it was still wet. The results were not great, but better than I expected. There is a bright spot toward one of the upper corners, caused by a hole in the top of the box that I had overlooked. There was either a little light leak in one corner, or it was caused by improper handling of the paper.
It's not a great photo, but it was terrific fun and a great learning experience. My ultimate goal is to be able to build reliable cameras that others can use, whether from found objects or built from scratch. Baby steps.