Having now decided that the best sort of camera for this project would be an action camera (for reasons of sensor size, flexibility and pricing), and that I was going to use D-Mount lenses, I needed to decide which camera to use.
In terms of camera options, I started with an evaluation of GoPro, because I know that it’s generally seen as the highest quality action camera, and that I could better assess other options once I knew as much as possible about their line of products. The first thing I noticed is that GoPros are definitely far more expensive than other action cameras, as it’s the big brand in the category. I bought a GoPro 4 Silver on Ebay that someone had tried to repair, and having given up on then sold it to me in pieces for $15. This let me see how the device was constructed (in aspects unique to the brand as well as how backfocus, etc was set up), and also gave me some parts that might be useful later in the process. One thing I quickly noticed about GoPro construction is that it is highly efficient and packed together tightly. This drove me see GoPro as a less than desirable candidate for the modification.
Spending a few days looking at action cameras and reading up on modifications, it became pretty obvious that Yi is most people’s second favorite action camera after GoPro. -Aside from some professional cameras that are more expensive than the GoPro, and some no longer manufactured, that could conceivably fall into that category. I also noticed, that. although quite small itself, the Yi 4K provides quite a good image and its internal components are less tightly packed than the GoPros.
Given this flexibility in the Yi, I decided that my first attempt at modification would be through the front of the camera, rather than going straight to a totally new housing. Philosophically, I tend to like a less destructive path, if possible. Below is a picture of the Yi after I removed the plastic front panel and cut away the aluminum surround that both held the lens mount in place and protected the lens. You can see two of the three wings of the grey plastic M12 lens mount now exposed in the gaps in the aluminum, which is now cut away.
This will give me freedom to either remove the M12 lens mount entirely, and have the new lenses mount only on the new front panel of the camera (which I’m designing and fabricating), or I can trim down the M12 lens mount, and adapt an M12 lens barrel to screw into it, so that an existing M12-to-D-Mount adapter I’ve designed and 3D-printed (SLA) will fit into it. The image below is of an earlier iteration, followed by a rendering of the one I have off printing now.
The lens mount approach really depends on some upcoming decisions and discoveries, but also how well the D-Mount lenses I have will fit into the gap in the front of the camera. D-Mounts have a diameter of 15.88mm, so conceivably, I can get the lenses down into the body of the camera a bit. The real benefit of doing so (if possible) is to help resolve the issue of D-Mount lenses having a flange focal distance (flange to image plane) of 12.29mm, which is quite close.
I made the tiny jig below to facilitate working with M12/S-mount lenses and conversions. The first thing I’ll need to do is decapitate an M12 lens so that I can use it (if necessary) to connect the camera’s M12 mount to the mount D-Mount adapter that’s currently being printed.