After doing some reading on the mrpinhole site and on other pages on the internet it is becoming increasingly apparent that the relationship between your cameras focal length and your pinhole aperture is very important and affects the quality of your final image quite severely. With this in mind I would like to have a go at making a camera, or at least having a camera made where these dimensions and figures are as accurate as possible. With the Ensign pinhole camera conversion the measurements of the cameras focal length were approximate, and I believe this is why the images were not as sharp as I expected. Above is a scale diagram of the top down view of what I have done so far. 50mm focal length which will be teamed up with a 0.3mm laser cut pinhole. These dimensions seem to offer the best chance of getting a sharp image. They allow for a large projected image onto the film so I shouldn’t get any distortion at the edges caused by a very short focal length.
View of the camera from the back with the back open/off. Inside will be an interchangeable set of masks to allow shooting in 6×9, 6×7 and 6×6 formats. I am not sure if I would use these formats, especially 6×6, but it seems like a waste to not incorporate them as I have the chance. The camera will also have two film advance knobs to allow the film to be rolled in both directions. Again, not sure if i’d need it, the only real reason I can see for it would be intentional accurate double exposures of certain frames, but, I can incorporate it so why not. When shooting pinhole I tend to note each frame in a notebook – subject, exposure, film etc so I could in theory roll back and shoot over a certain frame if I wanted to.
At the top I have noted film diagonals, this is the size of the diagonal of the negative. I have also noted that with a 60mm focal length the image diameter created is 115mm. This is the projected CIRCULAR image from the pinhole. 115mm is large enough to cover the 6×9 negative easily.
I have chosen the use of 120 roll film as I want to have large negatives. I could have designed the camera to use 4×5 or larger sheet film, but at the moment the use of sheet film is financially not available to me. I would also need to buy dark slides to use it so 120 roll, with a 6×9 neg is as large as I can reasonably go.
The larger the negative in theory the greater the detail that can be captured.
Quick sketch of the camera from the same angle with the back closed. The back will need three viewing windows covered with red plastic to allow me to read the frame numbers on the films backing paper. I may also try and come up with a way of covering these fully to prevent any light leaks. I do not think this is required, some of my 120 cameras have windows that you can cover, some don’t so I guess its not required. Just may be better if the film is in the camera for long periods of time?
May also incorporate the holder on the bottom right to put in a box label to remind me what film is in the camera. My Bronica ETRS has this on the film backs, I dont generally need it as I go through a whole roll when I am shooting something. I dont like to leave half used rolls in the camera and I like to develop them as soon as possible. Also if im shooting something for my university work I dont have time to just leave it until the roll is fully finished.