Identification and recognition

Conclusion

The ability to identify or recognize persons or objects depends on a number of factors. Some of the more important factors are:

  • Camera resolution and scene size

  • Lighting conditions

  • Camera position

  • Motion

  • Compression

Surveillance objectives determine the number of pixels a person or object needs to occupy in the captured footage. Axis recommends 80 pixels or more for identification in challenging conditions. For license plates, text should be 15 pixels vertically. Check legal requirements for footage intended as evidence.

The camera resolution determines the maximum size of the captured scene. The more pixels, the larger the scene covered. The camera’s depth of field is important in order to allow identification within a wider range.

Axis Lens Calculator is useful when selecting cameras to fulfill requirements for identification and recognition.

Identification might not be possible in challenging lighting conditions even if resolution is high enough. Highly sensitive sensors and features such as wide dynamic range can help, but also consider better lighting and positioning of the camera to avoid backlit situations.

Camera positioning is important in order to get distortion-free images.

Select an appropriate frame rate and shutter speed depending on the movements of your surveillance subjects.

Test your system under operational conditions to ensure that the installation meets your surveillance objectives. Review recorded footage to ensure that image quality has not been compromised by compression and that the quality is sufficient for your requirements.