Quelle est la différence entre les objectifs CCTV à focale variable et les objectifs CCTV fixes?

Les lentilles à focale variable sont un type d'objectif couramment utilisé dans la télévision en circuit fermé. (Vidéosurveillance) appareils photo. Contrairement aux objectifs à focale fixe, which have a predetermined focal length that cannot be adjusted, varifocal lenses offer adjustable focal lengths within a specified range.

The primary advantage of varifocal lenses is their flexibility in terms of adjusting the camera’s field of view (Champ de vision) and zoom level. By changing the focal length, the lens allows you to vary the angle of view and zoom in or out as needed. This feature is particularly useful in surveillance applications where the camera may need to monitor different areas or objects at varying distances.

Varifocal lenses are often described using two numbers, such as 2.8-12mm or 5-50mm. The first number represents the lens’s shortest focal length, providing a wider field of view, while the second number represents the longest focal length, enabling a narrower field of view with more zoom. By adjusting the focal length within this range, you can customize the camera’s perspective to suit specific surveillance requirements.

It’s worth noting that adjusting the focal length on a varifocal lens requires manual intervention, either by physically turning a ring on the lens or by using a motorized mechanism controlled remotely. This allows for on-site adjustments to suit changing surveillance needs.

The main difference between varifocal and fixed lenses in CCTV cameras lies in their ability to adjust the focal length and field of view.

Distance focale: Fixed lenses have a specific, non-adjustable focal length. This means that once installed, the camera’s field of view and level of zoom remain constant. On the other hand, varifocal lenses offer a range of adjustable focal lengths, allowing for flexibility in changing the camera’s field of view and zoom level as needed.

Field of View: With a fixed lens, the field of view is predetermined and cannot be altered without physically replacing the lens. Varifocal lenses, on the other hand, provide the flexibility to manually adjust the lens to achieve a wider or narrower field of view, depending on the surveillance requirements.

Zoom Level: Fixed lenses do not have a zoom feature, as their focal length remains constant. Varifocal lenses, however, allow for zooming in or out by adjusting the focal length within the specified range. This feature is useful when you need to focus on specific details or objects at different distances.

The choice between varifocal and fixed lenses depends on the specific surveillance needs of the application. Fixed lenses are suitable when a constant field of view and zoom level are sufficient, and there is no requirement for adjusting the camera’s perspective. Varifocal lenses are more versatile and beneficial when flexibility in field of view and zoom is desired, allowing for adaptation to varying surveillance scenarios.