Design of the Pinhole Camera
Pentax MX SLR
        Camera3X Scale Model of Pentax
          MX4 x 5 and 35 mm film sizes

I wanted the pinhole camera to be a scale model of my Pentax MX 35 mm SLR camera, and I wanted it to use 4 X 5 inch sheet film. So the first thing I did was compare the size of the film used in my Pentax and the much larger film to be used in the pinhole camera, as shown in the picture above.

The 4 X 5 sheet film is about three times larger in length and width, so I decided to make my pinhole camera a 3X scale model of my Pentax. Most scale models, such as airplane models and Earth globes, are smaller than the objects they represent. This scale model, however, is three times larger.

I measured the Pentax camera, tripled the length and width measurements, marked and cut  pieces of cardboard, and glued them together. The camera had to be sealed so that only the light coming through the pinhole in the front would reach the film. I needed to design a light-tight door that would allow the sheet film to be installed and removed.

I thought about making a "zoom lens," which would be a telescoping fitting that changes the pinhole-to-flim distance. However, I decided it would be too difficult to make the fitting entirely light-tight. So I built the camera using a fixed "focal length" (pinhole-to-film distance) of 150 mm, which is three times the 50 mm focal length of the Pentax camera. This resulted in a "normal" field of view for the photograph.

Next: Construction of the Camera

©2005 Gray Chang