Converting a film camera to digital, part 1 – selecting and preparing the camera

For my son Derek, the photographer, I decided to convert an old film camera into a digital camera using a Raspberry Pi Zero W and a PiCam. There are examples of this online (Instructables has a few good builds), so I had a good place  to start anyway. I really wanted to keep the vintage look and feel (no external battery, no external openings for USB ports, and retain the shutter mechanism for the sound), so it would be a more challenging build.

Finding the right donor

The first step was to find a suitable donor, so I went to the local antique store to do some shopping.

I kind of expected I’d strike out and end up buying something on eBay, but there were a lot of old film cameras there. Old Kodak Brownies were abundant and cheap, but they didn’t have the right look. Old Polaroids with the extendable lens and bellows practically screamed “I’m a camera!” and looked great, but they were too big for what I had in mind. There were a few really nice TLR (twin lens reflex) cameras with adjustable focus, shutter speed, and aperture but they were more expensive than I was looking for. And I would have felt slightly guilty cutting up a camera that could still take nice pictures for someone with the patience for film.

After wandering around for an hour I ended up buying the first camera I had looked at, a Kodak DualFlex II, for $20. Probably because I grew up in the 60s and everyone had these or something like them, it felt like the right camera to use. The size (around 3″ x 3″ x 5″) was about right too.

This camera turned out to be a great choice for a couple of reasons – the flash unit provided me with a switch in the body tied to the shutter mechanism, and the shutter had a ‘B’ setting for long exposures – the shutter stays open as long as the button is pressed. These cameras are also really easy to disassemble. The one drawback was the size – the Pi and PiCam would fit fine, but finding a battery that had enough power and would fit in the case would be difficult. The battery could be hidden in the detachable flash unit, but it added a lot of bulk that I wanted to avoid.

Disassembling the camera

This was easier than I had expected, mostly. Three screws on the bottom hold the back on and attach the bottom of the side rails.

4 screws around the viewfinder (under the hinged cover on the top of the camera) hold the top of the body together.

Once you remove all these screws, you can slide the sides back, and the camera comes apart (you may need to gently pry the gap between the sides and the front of the camera). Remember where everything goes, because once you get the side off the mirror for the viewfinder will come out. Next remove the 4 screws holding the nameplate around the lens.

Once everything is apart, clean the viewfinder glass, mirror, and viewfinder (top) lens. These things were around in the 60s, so they’re probably covered with a thick coat of nicotine and dried on martini fumes.

 

 

 

 Inside the camera, there is a black metal liner, probably a reel for the last roll of film used at the bottom, and a film take-up reel at the top. I only needed the part of the metal liner with the holes for the 2 top back viewfinder screws, so I used a Dremel to cut off the part I didn’t need.

I really have to respect those Kodak engineers – it’s a well designed camera that took decent pictures and was probably pretty easy and inexpensive to build. No shutter speed, f-stops, or focus to deal with, so easy to point and shoot. Probably not ideal for anything but holiday snaps, but great for that. No wonder there were so many around in the 60s.

 

 

 

 

 

The hardest part of taking this apart was getting the camera lens out. I could have just used a hammer and nail to break it out, but that seemed almost disrespectful and I was afraid of damaging the front plate. Bending open 3 tabs on the inside of the face plate that held the lens bezel in place allowed me to take out the lens in one piece. This took some time, the tabs were really pressed in there. Which makes sense, this is probably the only critical part of the assembly, since a misaligned, misplaced, or loose lens would ruin the focus. If I’d though of it ahead of time, I would have cut a round plastic piece to cover the opening. After removing the lens, put the bezel back in place and bend the tabs back.

Removing the inside shield exposed the shutter mechanism. This is when I realized that the flash unit saved me the effort of rigging a switch – there was already a switch in place for the flash attachment (lower left side of the body, looking in from the back)

All I had to do was solder wires to the inside of the flash unit terminals and I’d have a switch that closed when the shutter was open. Perfect!

 

I had to remove the inside shutter cover (the round metal part of the shutter mechanism) – I probably could have left it, but

 

getting it out of the way made mounting the PiCam easier. I also used a drill to make the aperture opening match the outside diameter of the PiCam lens. Again, probably not absolutely needed but it made lining up the PiCam lens with the aperture hole a lot easier.

 

 

One step I did later that would have been easier to do at this point as  to drill a small hole in the red plastic port on the back where the picture number would be displayed if it were using the original film. I ended up adding a 3 color status LED (on, ready to take a picture, uploading), but all 3 colors looked the same through the red plastic…

 

If you end up trying this, look for the ‘I/B’ switch. Without that I probably would have had to either remove the shutter mechanism or spend a lot of time fiddling with the timing of the shutter and the PiCam image capture. In the ‘B’ position, the shutter stays open as long as you hold the button. Just tell the user to hold the button for a half-second or so when taking pictures and a image capture switch rigged to the flash terminals will work just fine.

By the way, the exposed terminals for the detachable flash are the two posts at the bottom of the camera body, below and to the right of the ‘I/B’ switch in the picture on the right.

 

 

 

 

Reassembly

With the pretty minor case mods and cleaning done, the final prep step was to line up the mirror and shutter mechanism plate with the slots in the sides of the body, slide the sides back into the rails on the front plate, and replace all the screws. Replace the front plate and attach with it’s 4 screws, and you’re done.

Digital camera hardware and software

The next post will cover the much more complicated than anticipated Raspberry Pi software and hardware setup.

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