Wood Body Pinhole Camera - #2 Film Take-up Spool, Detail Drawings & Selecting Wood

With the pinhole lens, the shutter and the film can winder done the last piece to resolve is the winding or take-up side of the film management.  Rob and I had discussed a number of ways to attach the film and wind it each with their advantages and disadvantages.  However, none of them really stood out as the optimum solution.  Rob ended up taking apart a regular film can wasting the film to get to the spool and brought it by to see what I could do with it.

However, before I get into that below are a couple of photos, we took using the pinhole lens mounted on a digital camera before I cut it apart (the lens, not the camera 😊).  This one is of the prototype we have been using to test out the different parts. 

Here we were outside working to establish the angle of view.  There is a little flare but that is probably due to us shooting into the sun.

Back to the take-up spool.  After some experimentation a straight forward fairly simple method and assembly came together that looks like it will work.  Here is the end result with the film loaded and wound onto the take-up spool.

There are two items key to making this work.  First is to modify the film by cutting a small notch in the film leader.  That is shown below where you can see at the lower right of the film leader a small rectangle has been cut away.

Second is when I looked closely at the film spool there in the center slot were a few barbs that pinched the film holding it in place.  They held the film tight enough to allow it to be wound a couple of revolutions firmly securing it while allowing the film to be rewound back into the film can.  Here is the take up spool when the film is just starting to be wound.

With all the identified problems resolved it was back to the model to incorporate all of them into one final version.  The revisions started with the measured lens to film plane distance and worked out from there.  In the end every one of the pieces were revised and or moved.  Here is what the finished 3D model looks like.

The completed model represents the overall look of the project but the two exploded views below give an idea of all the pieces that will go into the finished product.

Now that the model is done or as least as much as can be until I get into the actual build it’s time to add dimensions and there a lot of them.  The model is set up with each piece on a separate layer.  What that means is if all the layers are turned off except for say the top that’s all I see.  Doing that makes it easy to concentrate on getting all the required dimensions on it.  Once I get a view angle that shows all the dimensions, I can print it out. 

With the top done, I can turn that layer off and turn on another layer in this case the front which makes only it visible.  Dimensions are added to it and the process continues until all the pieces are dimensioned.  Individual pieces with dimensions are printed out on their own page.  With some pieces like the front a couple of views are needed to catch everything.

I could print out all of the pieces at once and include all the needed dimensions but it gets really confusing so won’t do that.  At this point I believe most of the problems and questions that I can foresee in the project have been solved.  That’s not to say nothing will come up during the build but if or more likely when it does, I hope it’s relatively easy to resolve.  All said and done the design, revisions, discussions and testing of prototypes took the better part of a month.

First up in the build is material selection.  Rob and I had discussed varieties of wood that could be used.  Oak and mahogany were rejected as more porous than what I thought would look right.  The tropical exotics were also nixed from my concern on stability.  Regular maple as well as curly or birdseye were rejected because of a concern that as a light-colored wood it might show dirt unless a film finish like lacquer or polyurethane was used.  I was concerned about either of those finishes gassing off and reacting with the 35mm film emulsion.   We narrowed it down to cherry or walnut and as we discussed the aesthetics of the piece Rob asked for a contrasting secondary material to be used.  With that in mind we decided to use cherry for the body and walnut for the shutter assembly and winding knobs.  Both are fairly hard woods that work well and look good. 

To minimize wood movement and help keep the camera stable all the pieces selected are quarter sawn and have been in my storage area for at least 10 years so they are thoroughly dried.  Here they are.  If you look close at the front right piece of cherry it does say “WARPED”. 

That was not the only piece that needed a little help.  It and another one had a bit of twist plus one had a little cup.  A little work with the hand plane and a trip through the thickness sander flattened them out.

One of the walnut pieces still had its rough sawn edge but a few swipes with the hand plane gave me a nice straight edge to work from.

Another of the walnut pieces had its grain running diagonally across it and I wanted it parallel to the edges.  The solution is to mark a line parallel to the grain, in this case the top of the piece, then cut along the line with the bandsaw.  That’s followed by using the hand plane to smooth the cut.  Last is to take that new edge and cut a parallel edge on the table saw.

Next Up – Ripping to Thickness & Changing Bandsaw Blade

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