Digging out the various camera's and lenses I had, I set about testing different combinations. I was testing for zoom range and the minimum and maximum focus distance. Some of the options would require making a custom mount to connect the camera to the lens, and others would require purchasing adapters for the macro lens to be attached.

Here are some of the ones I tested:

The lens that I ended up choosing was the 18-108mm F/2.5 lens with C-mount shown on the left. This was easy to mount to both the frame and the camera, and had the widest zoom range, as well as an easily adjustable iris. It's main downside is that it did not have a focus motor built in, so if I want to have that, I'll have to add this myself.

I tried several camera, including an older webcam, and a laptop camera, but ended up with an older C-mount USB camera I had gotten awhile back for astrophotography use. It was just easiest to use and assemble, and it removable so I can still use it at the telescope. It is a 1400x1040 resolution camera, which works great with a 1080 monitor at 1:1 resolution.

Using a HD web cam would have worked just as well, just taken a little more work in mounting. It's smaller sensor size would have worked great with some of the electric zoom/focus lenses. The smaller sensor would make for a higher magnification, combined with the shorter focal length lenses, such as the 14-84mm. This would have resulted in similar magnification and provided motor control. I might reconsider this in the future.

This combination supported a focus distance range (in otherwords the working distance) of 4.5 inches to 13 inches. The 13 is perfect because it is the height that comes from mounting the camera low on the arm in the lower position. And I can use spacers to move an object closer to the camera for higher magnification use. It's also possible I could modify the arm to adjust to an even lower position as well.

Here is how the magnification works out at the extremes, assuming the image is being displayed on a monitor with 12" vertical height. Values between these are continuously adjustable via zoom or working distance.

I expect to mostly be using it with the camera at the full 13 inch height. This results in a zoom of 3.6 to 20, which is excellent for soldering.