CCTV lens is usual in daily life, here we’d like to share how to choose a suitable CCTV lens for your camera.
Firstly, to find out what kind of mount for your CCTV lens.
- C, CS or board, it depends on the camera or sensor that a lens works with, so to check your camera o sensor firstly.
- Board lens thread: M12x0.5, C or CS mount lens thread: 1-1/32”.
For the second, choose correct angle of lens.
It is important to understand the angle of the lens, the angle of view depends on the focal length.
• 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 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 (4.8×10/8).\
- 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 (4.8×165/8).
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.
Thirdly, compatibility between lens and sensor sizes.
- A 1″ lens can work with a 1″, 2/3″, 1/2″, 1/3″ or 1/4″ camera.
- A 2/3″ lens can work with a 2/3″, 1/2″, 1/3″ or 1/4″ camera.
- A 1/2″ lens can work with a 1/2″, 1/3″ or 1/4″ camera.
- A 1/3″ lens can work with a 1/3″ or 1/4″ camera.
- A 1/4″ lens only can work with a 1/4″ camera.
Fourth, fixed or adjustable focus.
If you need adjust the view of angle, you need choose a vari-focal lens. Otherwise, you can choose a fixed lens to save money.
Fifth, use auto-iris or manual iris?
- If the light condition changes, you will need an auto-iris lens or a manual-iris lens.
- An auto-iris lens can be adjusted iris by a camera. A manual-iris lens can be adjusted iris by hand.
- For example, if you got an outdoor camera, an auto-iris lens may be what you need. There are DC drives and video drive for auto–iris lenses. Most cameras can support both drive types. It can be selected by a switch on the camera.
Sixth, choice between an IR lens and a normal lens
- If you want to see clear images under IR LED illumination, an IR lens is the better choice.
- A normal lens might not perform as well because it is not optimized for infrared light wavelengths.
Eighth, if you like to see from a small hole, you can choose a pinhole lens.
Nineth, in what situations is an adapter needed?
If you have a CS mount camera and a C mount lens, you need to place a 5mm adapter between the lens and the camera. Otherwise, it will not work.
Tenth, when to use an Extension Tube for your CCTV lens
- Extension tube allow you to turn standard fixed focal length lenses into macro lenses.
- An extention tube kit is available which includes 7 extender tubes: 0.5 mm, 1 mm,2 mm, 5 mm, 10 mm, 20 mm and 40 mm for extension from 0.5 mm to 78.5 mm. The tube(s) mount between the camera and the lens, making it possible for you to focus a C or CS mount lens at a much closer distance than normal.
Finally, What is the function of the ring on the front of the camera?
There is a ring in front of most cameras so that you can adjust distance between the lens and camera chip if you need.
