Okay, for something completely different, I've been interested in the last few years about pursuing building a pinhead camera. This is a camera that uses a mirror the size of a pinhole, that projects a coherent image onto a film plane, instead of using a micro aperture.
I built two previous version of this. The first one was two pyramids made from thin cardboard, joined at their vertices, angled at 90 degrees from each other, with a small front-surfaced mirror at the corner painted black except for a pinhole-sized spot left shiny. It worked, sort of, with significant vignetting and a narrow angle of view.
The second version I tried to make it wider angle, and compatible with 4x5 film holders, but the design proved to be a failure because it permitted too much stray light to enter into the film chamber and fog the paper.
This third version uses the basic box structure from the second, but uses a small brass mirror box in an attempt to reduce fogging from stray light.
I'll now show the project being built in a series of pictures.
1. The pattern for the mirror box laid out in thin brass sheet:
2. The pattern cut out and bent into general shape, with aperture holes drilled and filed:
3. Blank piece of mirror. This was cut out from a large rectangle of front-surfaced mirror, salvaged from the lens assembly of an old projection TV, then cut with a glass cutter:
4.
The mirror painted with black paint, with a tiny spot left uncovered for the pin head mirror:
5.
The mirror glued to the mirror box, painted black:
6.
The camera layout, with the side-mounted lid removed. The large diagonal partition on the left is the divider between outside and inside. The light comes into the left, to the mirror box, then is reflected into the right hand area. The film plane is toward the front in this view. The other partition in upper right is a light baffle.
7.
Camera's side-mounted lid installed. You can see the opening into the mirror box. The insides of the camera box are covered in adhesive black craft felt. I used black gaffer's tape to affix the mirror box into a hole cut into the diagonal partition. Something more permanent will be used, once better results are obtained.
8.
The view looking into the film holder slot. I used wooden clothes pins as a way of providing clamping pressure for the sheet film holder. A bit crude, but the camera is light-tight.
First light. Not great results. Too narrow of an angle of view, and some fogging or internal reflections in the mirror box are evident. These are scans from paper negatives, and I had to manipulate brightness, contrast and curves to get any kind of usable images. Ah well, back to the old drawing board!
~Joe
1 minute exposure. A gravel path, with round step stones and a garden hose in the background.
16 second exposure. A while plastic drain pipe off the side of my storage shed.
Some additional thoughts. The black paint I used to cover the front-surfaced mirror appears pretty shiny. Perhaps a flatter finish of paint will reduce the haze and fogging.
As an alternative mirror, I could find a thin, stiff metal wire with the end already polished to a mirror finish. Or, polish the end of a wire to a mirror finish sounds like it would be very hard to do, hence my makeshift method of painting over a small piece of front-surfaced mirror.
As for the narrow angle of view, this will take some very intricate design and build to get a wider angle of view without stray light fogging the film. The reason I went with this very small mirror box was because version 2 of this camera used just a mirror mounted in a rectangular hole cut in the diagonal partition, and so much stray light was able to get through that the paper negatives came out solid black, even with the black felt and light baffles.
Hopefully there will be an elegant solution that will give me an adequate field of view (even 60 degrees would be enough) without fogging or flare. More design work is needed.
