Have you ever been confused about which focal length will perform better in different scenarios? How to choose between 4mm, 6mm, and 8mm lenses for specific purposes? Let's explore the relationship between focal length, lens, field of view, object distance and monitoring distance to make better decisions on choosing the best security camera. 

Starting with a simple demonstration below, where the y-axis is the focal length and the x-axis is the object distance.

The relationship can be summarized as: 

• The shorter the focal length →  the wider the field of view →  the broader the monitoring area 
• The longer the focal length → the narrower the field of view → the narrower the monitoring area

Here are some recommondations for common scenarios: 

• Elevators: limited range & wide field of view → 2.8 - 4 mm lens. 
• Outdoor environment: wide depth of field & wide field of view → 6 - 8 mm lens. 

• Garage/Warehouse: wide depth of field & narrow field of view → 6 -12mm lens. 

Monitoring distance calculation:

To calculate the approximate monitoring distance in meter for cameras with different resolution, check out the table below: (for focal length ≥ 4mm) 

For example, for a 2MP Camera with 4mm (N=4 in this case) lens, you can observe 

1. The feature of someone’s face and license plate easily in 6 meters (1.5*4=6);  
2. someone’s physical body features in 12 meters (3*4=12)  
3. someone’s movement in 24 meters (6*4=24). 

Note that the performance of a security camera not only depends on the features, but also the other factors like the work environment. If you would like to dig into a detailed guide on installing outdoor surveillance system, please check out:

Outdoor Surveillance Installation Complete Guide - Part 1
Outdoor Surveillance Installation Complete Guide - Part 2

or you can always contact us for any technical questions! Our in-house professional Tech Team is here to help.