Wood Body Pinhole Camera - #1 The Beginning

Several months ago, while I was busy with another project a friend (Rob) who belongs to the local camera club asked if I was interested in building a wood bodied pinhole camera.  Well, it was something I had never attempted but the idea intrigued me.  Once finished with the projects in progress we met for a little more in-depth discussion of what he had in mind.  After exploring several types and looking at the options we decided to pursue a camera that used 35mm film similar in concept to one made by ONDU.  

When I started working on the 3D model in SketchUp it quickly became clear that there were three items critical for us making the camera work. 

1. Designing a method of managing the film as in winding, re-winding and holding it in place during exposure.
2. Finding a suitable pinhole “lens” to insert into the wood body.  In the simplest terms that’s a very tiny hole in a piece of very thin metal. 
3. Some type of shutter to control the exposure.

All of those items needed to be accomplished without getting to deep into metal work as the equipment I have for metal fabrication is very limited.  Here is the first set of prototype renderings limited to preliminary case design and some rough dimensions.  At this point none of the three critical items had any resolution.

While Rob worked to source the pinhole “lens” I started on the film management part to see about coming up with a method to hold the unexposed film in place and be able to rewind it back into the film can once exposed.  After some trial and error using MDF and plywood prototypes this setup looks like it will work well for the film can end.   A slotted shaft is glued into a turned knob that has a steel washer inlayed in its base.  A couple of rare earth magnets are countersunk into the top which will mate up with the washer in the handle holding everything in place while allowing easy removal to change the film.  At this point we were still in discussion on how to take care of the winding side of the film.

Working on the shutter came next.  Reverse engineering from what I could see on the ONDU camera I put together a fairly simple metal shutter assembly.  Unfortunately, when going through what it would take to build the machining was just beyond my shop’s capabilities.  The renderings below show an exploded view and an installed view.

My next attempt was to design a sliding shutter out of wood.  Below is what an exploded view of that looks like.  There is a central slider captured by a pair of rails that uses a combination of rare earth magnets and metal bars to hold the slider in the desired location; either open or closed.  One thing with a pin hole camera is that the exposures are long so there is no need for a fast acting style shutter.

The top rendering below shows the shutter closed and the one on the bottom shows it open.  The good news is when I built a prototype the slider was held securely in place. 

Actually, it was held in place a little too well as moving the slider was pretty hard.  The four rare earth magnets and the steel plates provided a little too much grip.  A redesign that eliminated the metal plates and one of the magnets did the trick.  The slider was held in place either open or closed depending on how the magnet in the slider piece aligned with the two in the front of the camera.  Here is the redesign.

Not long after the shutter design got resolved Rob brought by a couple of pinhole assemblies that would attach to a modern Canon digital camera.  The information that came along with the it gave an f/stop of 223 and a Focal Length of 49mm which closely matched the 49.6mm measured on the camera.  We spent some time taking photos with it to determine the angle of view so that it can be added to the camera body later.  The angle at 41° equates to a moderate wide-angle lens.  Here is what the assembly looks like.

The pinhole assembly is made up of a black plastic housing that is designed to attach to the digital camera body where a typical camera lens goes and the metal pinhole “lens” itself.  We only need the actual metal pinhole.  However, getting it separated from the plastic mounting ended up not being pretty.  After about 45 minutes of non-destructive trying to unscrew the pieces with absolutely no luck I moved on to more non-reversable methods.  What finally worked was using a Dremel tool with an abrasive cutoff wheel to split the plastic. 

Once that was done and the plastic removed, I could get a good grip on the parts and it came apart fairly easily.  Bad news was while trying to unscrew the pieces the pliers did chew up the outer edges a little. 

Cleaning that up required me to turn a wood mandrel on the lathe so that I could friction fit the piece on it to clean the outer edges up.   The photos show the piece being jammed onto the mandrel.  A flat plate applies the pressure to the piece and sets it square to the lathe’s axis. 

Once the piece is mounted square, the flat plate and tailstock are pulled back out of the way so I can carefully file the edges smooth then polish to get rid of the scratches.

The last step is to cut a couple of shallow notches in the threaded retaining ring to provide a way of gripping it to allow ease of assembly and disassembly during testing.

Since this pinhole assembly is quite a bit larger and designed differently than what I had expected the mounting method needed to revised.  Here are front and back photos of the final test piece.  In the back view the notches cut in the mounting ring are easily visible.

Also, because the pinhole assembly was much larger in diameter than expected the shutter needed to be revised.  The revisions included a wider center sliding section and the relocation of the rare earth magnets.

Next Up – Film Take-up Spool, Detail Drawings & Selecting Wood