1. To find out what kind of mount for your CCTV lens, C, CS or board. It depends on the camera that a lens works with. Check your camera first.
Board lens thread: M12x0.5, C or CS mount lens thread: 1-1/32”.
2. It is important to understand the angle of the lens. The angle of view depends on the focal.
• The larger the number focal, the narrower the angle of view.
• The sensor of camera (h×v ):
1” sensor: 9.6mmx12.8mm
2/3” sensor: 6.6mmx8.8mm
1/2” sensor: 4.8mm X 6.4mm
1/3” sensor: 3.6mm x 4.8mm
¼” sensor: 2.7mm x 3.6mm
• The formula:
F = v X D /V or f = h X D /H
f: the length of focal
H: the height of the object
V: the width of the object
D: the distance between the camera and the object
h: the height of the sensor in camera
v: the width of the sensor in camera
Example 1, you want to watch an object 8ft wide (V) at 10 ft(D) with 1/3" camera (v=4.8mm). You need a 6mm focal lens (4.8x10/8).
Example 2, you want to watch an object 8ft wide (V) at 165 ft(D) with 1/3" camera (v=4.8mm). You need a 100mm focal lens (4.8x165/8).
That means the object is displayed by full screen on your VGA monitor.
If you do not know where you like to see, you can choose a varifocal lens, for example, 5-100mm, 6-60mm, 3.5-8mm, or 2.8-12mm, 5.5-33mm lens, etc. so that you can adjust the focal to find the best view.