First we can look into the appearance of the camera. Normally the dimension of camera with fix lens is less than camera with vari-focal lens. Meanwhile the vari-focal camera has auxiliary components, such as iris control, motor, gear. Secondly we can refer to specification of lens. Generally the focal length of fixed camera is a fix value, shown in the picture below:
| Items | Description | Tolerances |
| Focal Length | 3.6mm | ±5% |
| Aperture (D/f) | F2.0 | ±5% |
| Image Circle | 1/2.7" | >6.9mm |
| Focus Range | 0.3m~INF |
While the focal length of the vari-focal camera is a range of value, shown in the picture below:
| Items | Description | Tolerances |
| F No. | 1.5 | ±5% |
| Focal Length | 3.6-11mm | ±5% |
| Optical Back Focal Length | 6.24mm (In Air) | ±0.1 |
| Mechanical Back Focal Length | 13.20mm (In Air) | ±0.1 |
| Image Circle | 9 |
