When shopping for surveillance cameras you will notice that there are different camera lens types available. Each type of lens will provide a different field of view and some adjust to varying light conditions better than others. The main specifications you need to consider when choosing a lens type are focal length and iris.
The focal length of a lens is the distance between the lenses to the point at which the image is focused. This is typically measured in millimeters (mm). There are many different focal lengths available and most security cameras will come in either varifocal or fixed lens options. Cameras with a fixed lens have a set aperture that can’t be changed. The aperture is the space through which light enters the camera and needs to be adjusted to provide a wider or narrower view. If you have a fixed lens camera you will not be able to adjust the angle or range unless you physically move the camera itself. With varifocal lens cameras the aperture can be adjusted quickly and easily. For example you can go from a 2.8mm lens to a 12mm lens without moving the camera.
To better understand the difference between a 2.8mm lens and 12mm lens, refer to the images below. A 2.8mm lens will provide a wider angle with less detail while a 12mm lens will provide a narrower, more detailed view. The larger the lens size the farther it will view. The drawback to a 12mm lens is that the horizontal view narrows to as little as 15 feet.
2.8mm v 12mm
The standard focal length of a fixed lens camera will be a wide angle 3.6mm lens. These are designed to provide a 90 degree field of view, and provide effective surveillance in a 30 x 30 foot area.
Another thing to consider when purchasing surveillance camera lenses is whether or not is has an auto iris. An auto iris lens automatically adjusts the opening of the iris to adapt to varying light conditions which is very important for capturing clear images 24/7.
Remember to consider your specific needs when shopping for a surveillance camera. Make sure the camera has the right specifications to capture the field of view and light conditions of your location. If you are not sure or if conditions at your location may change then we recommend using a varifocal, auto iris lens as this can adapt to your environment.