C-Mount Lenses
| Manufacturer | Model | Sensor Size | Type | Focal Length (mm) | Aperture | Filter Thread (mm) | Blades |
|---|---|---|---|---|---|---|---|
| Canon | V6x17 | 1” | Varifocal | 17-102 | 2.0 | 58 | 6 |
| Fujinon | CF8A | 1” | Fixed | 8 | 1.8 | 52 | |
| Fujinon | HF9A-2 | 2⁄3” | Fixed | 9 | 1.4 | 46 | |
| Fujinon | CF12.5A | 1” | Fixed | 12.5 | 1.4 | 52 | 8 |
| Fujinon | CF25B | 1” | Fixed | 25 | 1.4 | 40.5 | |
| Fujinon | HF35A | 2⁄3” | Fixed | 35 | 1.7 | 49 | 6 |
| Fujinon | HF35A-2 | 2⁄3” | Fixed | 35 | 1.7 | 43 | |
| Fujinon | CF50B | 1” | Fixed | 50 | 1.4 | 49 | 10 |
| Fujinon | CF75A | 1” | Fixed | 75 | 1.8 | 49 | 10 |
| Computar | H3616 | 1⁄2” | Fixed | 3.6 | 1.6 | 35.5 | 3 |
| Opticom | Fixed | 8 | 1.3 | 40.5 | 6 | ||
| Cosmicar | H612A | 1⁄2” | Fixed | 6 | 1.2 | 40.5 | 6 |
| Cosmicar | C815B | 2⁄3” | Fixed | 8.5 | 1.5 | 40.5 | |
| Cosmicar | B1214D-2 | 1” | Fixed | 12.5 | 1.4 | 40.5 | 6 |
| Computar | V5018 | 1” | Fixed | 50 | 1.8 | 43 | 3 |
Adapters
The Pentax Q is the perfect camera for use with C mount lenses. With it’s flange focal distance of 9.2 mm, C-mount lenses with a flange focal distance of 17.526 can be easily adapted to the camera.
There are two adapters commonly available, an adapter consisting of a single machined piece of aluminum, and another that is constructed of two pieces of aluminum joined with set screws.
The one piece adapter:
The two piece adapter:
The one piece adapter seems to be more common, but it is the worse choice. It is almost 2 mm too thin, C-mount lenses used with this adapter will often need shims to be able to focus at infinity. The two piece adapter is much closer to the correct thickness, and most lenses will work without shims. The one piece adapter also doesn’t provide facilities for “clocking” the lens so that the focus and aperture markings are facing up, the two piece adapter makes this easy. Many C-mount lenses have set screws that can be loosened to allow the lens to rotate around the mounting threads, but it’s much more convenient to do it on the adapter.
Focus at Infinity
On forums I often see discussions about shimming C-mount lenses to achieve focus at infinity. On most lenses, adjusting the infinity focus is quite easy and removes the need for messing with shims. With many lenses, there are three small set screws near the front of the lens that can be slackened to detach the focus ring from the lens element. I will turn the ring to infinity focus, slacken the screws, then move the now-free ring to the middle of the focus range, then tighten one screw. Now I have a focus range that is shifted to half way past infinity. I find the infinity focus point, then loosen the one tight screw, reposition the ring so that the infinity stop is in contact with the stop on the lens body, and tighten three screws again.