As we know, there are various types of CCTV projects, among which we can highlight perimeter protection, LPR, access control, and forensic investigation as the main types sought. However, in addition to these numerous branches, each of these projects can be applied in various monitoring environments, generating multiple types of equipment and configurations.
This diverse range of equipment in the CCTV market can become a significant problem for a professional who lacks experience in the field. Therefore, in this article, we will detail tips for finding the right equipment and avoiding unnecessary costs through definitions of focal length, lens formats, and sensors.
Focal Length
The focal length defines the angle of view captured by a camera, where the smaller the focal length number, the larger the lens opening.
In the CCTV market, this configuration is generally classified in millimeters, where, for example, a distance of 50 mm has more opening than a distance of 200 mm, as shown in the image below:
Additionally, these lenses can be classified into two types: fixed and varifocal.
As highlighted in the following article, the main difference between the two types is the classification of focal length, where in the first example, the focal length is fixed, meaning if the lens is rated at 28mm, it will only support that angle.
In the second case, varifocal lenses are found in the market with definitions like 50-200mm and can be adjusted within the defined angle. Furthermore, the difference between the minimum and maximum focal length is the result of the amount of zoom that the varifocal lens provides.
Sensors
Basically, when we talk about image sensors, we can mention the two main types: CCD (Charge-Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor). This device found in cameras with digital technology is responsible for capturing the light of the image. The main difference between CCD and CMOS is that the former is compact and uses a less robust technology, which is ideal for home equipment, while the latter model of sensor is indicated for professional cameras.
The final definition of the image captured by the lens is influenced by the number of pixels that the image sensor captures; the greater the number, the better the definition.
Image Sensor Sizes
The measurement factor for improving recording quality is the choice of models with larger sensors, as they directly influence the number of pixels captured. There are some metrics for distinguishing sensor models, see below:
Sensor - Width - Height
1/3 - 4.8mm - 3.6mm
1/2 - 6.4mm - 4.8mm
2/3 - 8.8mm - 6.6mm
4/3 - 18mm - 13.5mm
APS - 22.2mm - 14.8mm
FullFrame - 36mm - 24mm
How to Choose?
As specified in this article, there are various configurations and metrics that can influence the choice of equipment. Ideally, the professional should measure the monitoring area to check the focal opening distance and the minimum zoom necessary to obtain quality images for their project.
Sensors are related to the quality of image capture and can enhance the lens opening and viewing quality. However, generally, sensors like the 1/3 and 1/2 CMOS are the most commonly used in the CCTV market due to the balance of resolution, transmission bit rate, and storage. Although there are sensors with larger capacities like FullFrame, these are intended for the professional photography market.
