Modifying the Tektronix C-12 for a Cannon Digital Camera

The Tektronix C-12 camera originally used a Polaroid camera back and Polaroid film.  The film is no longer available and even if it was the steps required to scan the paper photo to include in documents would be tedious and time consuming.  The body of the C-12 is beautifully crafted and lends itself nicely to be a mount for a cheap digital camera. These are some notes on the steps I took to do the conversion.

fig.1 Here is the C-12 after conversion

After removing all of the parts associated with the Polaroid camera you will be left with a backing that used to hold the film back. At the top of the plate there is a silver pull tab that allows you to remove the plate.

fig.2 This shows the pull tab and backing

Once the backing is removed I cut two pieces of metal to attach to the backing. One is a flat piece of tin that acts as a light baffle around the lens of the camera.  The other is a piece of right angle aluminum that will be the shelf to hold the camera. I first attached the flat piece and located the center of the square hole in the backing. There I used a Greenlee punch to make a hole for the lens

fig.3 Attach the plate to the backing and punch the lens hole.

Next I placed the camera face on the plate so the lens is centered on the hole. I then taped the camera to the plate.

fig.4 Center the camera and tape it in place

After the holes have been marked and drilled I filed the two outside hole into a vertical oval so the camera shelf could be rotated a small amount to perfectly align with the scope reticule.

fig.5 File the outside holes to allow alignment

When the Polaroid camera was removed so were the camera bellows.  To replace them I cut a 2” long piece of 3.5” black ABS sewer pipe to act as a light shield.

fig.5 Add sewer pipe light baffle

It’s worth noting that there is an additional feature on the Tektronix C-12. There is a plate on the bottom that can be removed and replaced with a small light box. The intent was for the user to add custom film reticules that would be superimposed over the scope image. Here is a picture of the bottom plate removed.

fig.6 Bottom plate removed from the C-12

Here is the Projected Graticule that attaches to the bottom of the camera.  My idea as a follow-on project is to attach a small LCD to the opening so that scope pictures could be annotated on the spot using something like a Raspberry Pi or Arduino. The one trick to this is figuring out how to make the LCD a mirror image.

fig. 7