Selecting the Right Focal Length for Surveillance Cameras

At OHWOAI Surveillance, we recognize the significance of choosing the perfect focal length for your surveillance camera requirements. The focal length, measured from the optical center of the lens to the CCD/CMOS sensor in the camera, plays a crucial role in determining the image size, field of view, and depth of field.

Field of View and Depth of Field The field of view refers to the maximum range of observation achievable through the lens, formed by the two edges of the lens capturing the target object. On the other hand, the depth of field represents the range of distance in which objects can be captured in sharp focus.

Different Effects of Varying Focal Lengths In today's era of network surveillance cameras, the focal lengths commonly available range from 2.8mm, 3.6mm/4mm, 6mm, 8mm, 12mm, to 16mm. Some cameras even offer variable zoom functionality. But what are the differences brought about by different focal lengths?

Here's a simplified breakdown:

✅ Larger focal lengths allow for long-range observation but offer a narrower field of view.

✅ Smaller focal lengths enable closer observation with a wider field of view.

✅ Larger focal lengths provide clearer details, but the observed field of view is reduced.

✅ With the same focal length, objects at a greater distance can be captured within a wider field of view, albeit with lower recognition accuracy.

✅ Larger focal lengths are necessary to capture clear images of faces or human forms from a greater distance.

Choosing the Right Focal Length for Surveillance Cameras To make an informed decision, consider the following factors:


Monitoring Range The focal length of a surveillance camera determines the size of the monitoring image and the effective visual distance, which translates to the monitoring range. ☆ For smaller monitoring ranges with a larger field of view, such as in residential living rooms or small retail shops, cameras with smaller focal lengths like 3.6mm or 4mm are suitable. These lenses offer a viewing angle of 75°-90°, allowing coverage of spaces ranging from 40² to 80². ☆ For larger monitoring ranges, such as spaces larger than 10m x 10m, cameras with larger focal lengths are required. However, due to the larger focal length, the corresponding field of view becomes narrower. To achieve comprehensive monitoring, consider using pan-tilt-zoom cameras or installing multiple surveillance cameras for complete coverage. ☆ For fixed monitoring ranges but very long distances, such as monitoring a parking lot 30 meters away, opt for cameras with focal lengths greater than 12mm.



Usage Scenarios Many times, the selection of surveillance cameras is based on specific scenario requirements. If you prefer not to delve into complex focal length parameters, you can roughly determine the camera focal length based on the following usage scenarios:

✅ For small and confined spaces like garages or storage rooms, we recommend a 2.8mm focal length, providing optimal monitoring within 3 meters.

✅ In indoor home environments or small-scale retail stores, a 4mm focal length is recommended, offering optimal monitoring within 3-5 meters.

✅ For outdoor scenes such as home gardens, balconies, or entrances, a 6mm focal length is advised, ensuring optimal monitoring within 5-10 meters.

✅ In outdoor locations like roads or alleyways, an 8mm focal length is recommended, providing optimal monitoring within 10-20 meters.

✅ For certain fixed long-distance monitoring situations, a 12mm focal length is recommended, providing optimal monitoring within a range of approximately 20-30 meters.

✅ Some cameras feature adjustable focal lengths, allowing you to customize the lens size based on the monitoring scene's range.


At OHWOAI Surveillance, we offer a wide range of surveillance camera systems tailored to your specific needs, including indoor and outdoor IP camera modules, PoE security camera sets, wired security systems, commercial security camera systems, outdoor NVRs, Funlux security camera sets of 4, PoE home surveillance systems, and Zmodo NVR PoE solutions. With our advanced technology and comprehensive product lineup, you can trust OHWOAI Surveillance to deliver high-quality surveillance solutions for your peace of mind and security.

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