Choosing the Right CCTV Lens
Proper lens selection is crucial for CCTV effectiveness. Learn focal length, sensor compatibility, and how to match lenses to your requirements.
Understanding Focal Length
Focal length (measured in millimeters) determines the lens's field of view. Shorter focal lengths (2.8-4mm) are wide-angle and show more area. Longer focal lengths (25-50mm) are telephoto and zoom in on distant objects.
Focal Length Ranges:
- 2.8-3.6mm: Wide-angle, 80-110 degrees FOV
- 4-8mm: Standard, 50-80 degrees FOV
- 12-25mm: Telephoto, 15-50 degrees FOV
- 35-50mm: Very telephoto, less than 15 degrees FOV
Lens Categories
Fixed Lens
Lens focal length is fixed and cannot be changed. Cheaper, simpler, but less flexible. Most common in CCTV.
Varifocal Lens
Focal length can be adjusted (e.g., 2.8-12mm). More expensive but allows fine-tuning after installation.
Motorized Zoom
Focal length is electrically adjustable. Most expensive but allows remote adjustment from control room.
PTZ (Pan-Tilt-Zoom)
Camera can pan, tilt, and zoom. Used for active monitoring, not typical fixed surveillance.
Sensor Size Matching
Lenses are designed for specific sensor sizes. Using the wrong lens on wrong sensor size can cause image vignetting (dark corners) or inadequate coverage.
| Sensor Size | Common Lenses | Application |
|---|---|---|
| 1/3 inch | 2.8-50mm | Standard surveillance |
| 1/2 inch | 3.6-50mm | General use |
| 2/3 inch | 4-100mm | Specialized systems |
Lens Selection Guide
Wide Area Coverage
Use 2.8-3.6mm wide-angle lenses. Covers large spaces but with lower detail. Good for detecting motion across wide areas.
Facial Recognition
Use 4-6mm lenses mounted 2-3 meters from faces. Provides good detail without being too narrow.
License Plate Capture
Use 12-25mm telephoto lenses. Position 15-30 meters from parking area to capture plates clearly.
Perimeter Security
Use 6-12mm lenses on poles or building corners. Balance between area coverage and detail.
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