CCTV Security Camera Lens
How to Select most suitable Security Camera Lens?
7 important Factors
Now let’s start to touch on the complexity of security camera lenses and walk through the top 5 can’t-miss factors when selecting the best lens for security cameras.
1. Focal Length
The security camera lens size, or focal length, measured in mm, is an important term in security camera lens and determines the field of view, also called the viewing angle for a particular camera lens.
So what’s the difference between CCTV camera 2.8mm lens, 3.6mm lens and 12mm lens security cameras?
In short, the smaller the security camera lens focal length number is, the wider area you can see but in lesser details; the bigger the focal length, the further you can see, but with narrower viewing angle.
The security camera focal length can vary from wide angles that can take in an entire landscape to security camera telephoto lenses which can zoom in on a small subject in the distance.
Taking ZOSI security camera lens for example, the wide angle lens security camera ZOSI IPC-2612D with the 1/3″ CMOS sensor and 4.0mm focal length features a wide field of view (horizontal: 80°, vertical: 42°) to cover the areas you need to monitor.
Hint: The security cameras with wide angle lens work best for large-area places such as the parking lots, back yard, warehouses, construction sites, etc.
While the narrow angle lens cameras are ideal for critical entrances, like the doorways, hallways, cash registers, etc.
2. Aperture
The aperture of security camera lens is the hole that light passes through to enter the camera, which is measured in f-stops.
What might be confusing, however, is that a lower number of f-stops represents a wider aperture. Say, f1.4 is a large aperture and allows for more light to pass into the camera.
The aperture is a significant term for security camera lens because it can affect the camera’s depth of field — the distance between the nearest and farthest objects in a scene that appear sharp in an image.
The narrow aperture corresponds with large depth of field, which contributes to more objects captured in focus.
Hint: You can control how much of a scene is in focus by adjusting the security camera lens aperture. A wide aperture will make objects in front of you well focused but the background blurry. Whereas a small aperture will lead to everything captured in focus.
3. Iris
Aperture, measured in F numbers, is the camera’s ability to gather light. The lower this F number is, the larger the lens aperture will be, the more open your lens, and the better it will be at allowing light to pass through and onto the CCD image sensor. For example, if you see the lens has a low aperture of F1.2, then it will work well in low lit situations. Consider your eye, how your pupil will dilate or contract depending on how much light there is. If you’re in a particularly dark area, your pupil will dilate to allow more light so that you can see better.
The iris controls how much light comes through the lenses’ aperture. When the iris creates a large opening, more light can pass through.
However, it is not the case that the wider the iris, the better images you can get. Too much light can wash out your video and you little light makes the scene dark.
So it is vital to pick up a suitable iris type for your purpose. The fixed and manual iris lenses are typically used for indoor environment where the light stays consistent, such as an office, school or shop.
The auto iris lens, on the other hand, can automatically adjust light changes and is more ideal for outdoor locations where there are light variations.
Hint: Think about where you are going to position the security cameras before diving into the security cameras lens purchase. Indoor or outdoor? That will influence the final iris types you pick up.
4. Manual vs. Auto Iris
This is very similar to the choice between Monofocal and Varifocal, in that one is fixed and the other “varies”, and thus, is more expensive. The iris has to do with how much light is allowed to filter in through the lens. A manual or “fixed” iris lens is one you’d use if you are in an area where the lighting does not change, like an office. An auto iris lens will automatically adjust for light variations. You’ll probably need an auto-iris lens for outdoor surveillance.
Also important for various lighting conditions, is the camera’s LUX rating.
5. Camera Format
When you look at the listed specification of security camera lenses, you will notice the numbers such as 1/2″, 1/3″, 2/3″, 1/4″ for the image sensors.
Generally speaking, the smaller the camera format is, the narrower the security camera lens field of view is. For example, a 2/3″ image sensor will see wider than a 1/3″ one.
That’s the format size of security cameras we are talking about. For lens format size, note that the lenses’ image format, say “2/3 inch image format”, is the maximum size it will allow.
So bear in mind that the format size of a security camera lens should be equal or greater than that of cameras, otherwise the corners of the scene being viewed will be cut off.
Hint: Remember to double check the format size of both security cameras and lens and follow the rule above to get great shot.
6. C or CS Mount
When mounting a lens to a CCTV security camera, you’ll have C or CS mount to choose from. Both the lens and the camera will specify which they are. Many cameras say “C/CS mount”, which means it will allow for either.
The difference between the two is the distance between the image sensor and the lens…
C Mount – 17.5mm
CS Mount – 12.5mm
C and CS mount are two available options when it comes to security camera lens mount, whose main differences lie in the distance from the image sensor to the lens.
The distance for C Mount is 17.5 mm while the CS Mount is 12.5 mm.
Hint: When selecting the lens for security cameras, check whether the lens and security cameras allow for C Mount or CS mount. Not having the matching lens could be responsible for the inferior images of security cameras.
7. Monofocal vs. Varifocal
Monofocal lenses or “fixed” lenses can only focus at a specific distance… “mono” –> one –> one length! They will have one focal length, like 16mm or 3.6mm. They are generally cheaper than Varifocal lenses, which will allow you to adjust the focal length manually. Varifocal lenses will usually have a range, like 2.5-6mm or 5-50mm. Zoom lenses are similar to varifocal, except the focal length will adjust electronically, thus they are generally more expensive.
