Homemade lens

Browsing the internet for photography related DIY projects, I found some articles on making your own lens, so I decided to try it. I had an old magnifying glass sitting around with a lens that was about 50mm in diameter. I cut off the plastic handle of the magnifying glass with a hack saw and filed off the rough edge.

Now I needed a way to mount it to a camera (first project was a Fuji X-E2) and some sort of tube that would extend it to the right focal length. Maybe a tube with a helicoid in it so I could focus at different distances. And maybe something to control the aperture, as a single lens element was not going to give me very sharp pictures wide open.

I found an iris diaphragm on eBay with an M42 mount on it. That was great because the external diameter of the Iris was close to the outside diameter of the lens, so I could just use gaffer's tape to attach the magnifying glass lens to the iris. The M42 mount is very common and I knew I would be able to find an M42 to Fuji adapter.

I figured out the approximate focal length by pointing the lens out a bright window at the sun and moving a piece of paper behind it until the sun was focused on the paper. Of course I didn't hold it long enough for the paper to start burning like I did in my childhood magnifying glass experiments. The focal length was about 80mm.

Knowing that the focal length of the lens was 80mm and that the aperture iris was 15mm deep and that the flange to sensor distance on A Fuji X camera is 17.7mm, I needed to add another 48mm to the length of my lens to get infinity focus plus more to focus closer. I found an M42 to Fuji extension tube on Amazon with a helicoid that would extend from 25mm to 58mm and cover the 48mm I needed.

I wanted to mark the helicoid for focal length and the iris for aperture. Focal lengths were just a matter of putting the camera on a tripod and pulling out a tape measure and selecting objects at 2 feet, 3, 7, 10, 30 and infinity and then marking them on the helicoid with a white marker. For the f stop values, I set the X-E2 to a fixed ISO, let it automatically compute the shutter speed and then used my light meter to find the equivalent F stop for that shutter speed.

And here are examples at narrow aperture versus wider aperture