Lens Selection

The viewing angle of a lens is called the field of view or FOV, and is determined by the focal length of the lens. Focal length is measured in millimeters. The larger the focal length in mm, the smaller the viewing angle of the lens. A 2.5mm lens would be considered a wide angle lens, while a 100mm lens will give you a long range, narrow field of view.

Lenses are broken down into two main categories; varifocal and fixed lenses. A Varifocal Lens is a lens that has an adjustable focal length. A fixed lens has a fixed focal length. When choosing a fixed lens, you must determine the focal length needed to get the footage you want. With a varifocal lens, you can adjust the focal length within the range of the lens.

The chart below shows the FOV of each lens based on its focal length. Keep in mind that a smaller FOV means a tighter, longer range view. So, you would use a higher focal length lens to view objects that are far away and a smaller focal length for objects that are closer.

Focal Length of Lens Field of View (FOV)
   
Fixed Lenses  
2.5 mm 75 degrees
4 mm 49 degrees
6 mm 34 degrees
8 mm 25 degrees
12 mm 17 degrees
   
Varifocal Lenses  
2.8-12 mm 68-17 degrees
3.5-8 mm 56-25 degrees
5-100 mm 40-2 degrees
6-60 mm 34-3.5 degrees