Spytronic

Surveillance and High Security

Lens and Field of vision calculator

Optical lens do play a critical role within the conception of a surveillance system. Their primary objective is to reflect images from a scene and to put emphasis on the lightning in order to obtain a clear and defined image. Typically, the more light passes trough the lens, the better the quality.

The selection of an appropriate lens is critical. It will affect the size, the shape and the clarity of an image. Factors like distance from the scene, focal length, required field of view, lightning and the size will affect the dimensions and clarity of the camera and that is why choosing the appropriate lens is necessary even if too often neglected by many installers with a lack of experience and knowledge in surveillance technologies.

Field of View

The field of view is produced by a specific lens and reflected by the actual image (width & height). If the field of view obtained is not the one desired, you may consider using a different one (angle, width, telephoto, etc.). to increment or decrement the field of view. Some tables are available to calculate the size of the image, the lens and the distance all combined to obtain de required field of view.

There are two different types of lens, fixed or varifocal. The fixed lens possesses a fixed focus. The varifocal lens is adjustable. The focal length is simply the distance from the optical center of the lens to a focal point close to the back of the lens. This distance is written on the lens (in mm) et indicates the field of view produced by the lens.

Image description of a field of
  view of a camera

Calculate the field of view

Enter the format of the chip (board), size of the lens and the distance from the objective
CCD/CMOS Chip Format  1/2"
 1/3"
 1/4"
Lens Format  mm
Distance from the Objective  feet
Angle of View  degrees
Height  feet
Width  feet

Calculate the Lens Format

Enter the format of the CCD chip, the distance from the objective and/or the required height and width
CCD/CMOS Chip Format
 1/2"
 1/3"
 1/4"
Distance from the Objective  feet
Minimal Width  feet
(Or) Minimal Height  feet
Lens Format