Use the IPVM Camera Finder.
Here are my results:
- ACTi - B51:
- Fixed focus = 1.9mm lens
- AoV = 129 degrees
- Arecont - AV5255PMIR-SAH:
- Varifocal lens = 3.0 - 8.0mm
- AoV = 43 - 113 degrees
- Hikvision - DS-2DE4220:
- Varifocal lens = 4.2 - 94.0mm
- AoV = 3 - 58 degrees
An interesting find on the Hikvision DS-2DE4220; the widest angle at 4.2mm is only 58 degrees while the telephoto angle is 3 degrees. That is a very tightly zoomed shot.
In the camera finder, locate the camera you want to report on and click on it to open a new page. Scroll down and locate the 'Lens / Imaging' section, this is where you will find this information.
You can choose any 3 cameras you like. The lenses can be fixed, varifocal, motorized, etc. Report any interesting observations or questions that come up as you are researching this.