Designing for Evidence Capture

Frame rate determines how often frames are sampled. Shutter speed determines whether each frame is sharp. Motion blur occurs within a single frame and cannot be repaired by sampling more frames or applying AI.

For reliable identification: Faces typically require 1/250 of a second or faster, and vehicles and plates often require 1/500 to 1/1000 of a second.

Shutter speed determines evidentiary value, so if shutter speed is critical, why not maximize it at all times?

To sustain fast shutter speeds, more photons must reach the sensor within that limited window.

Two levers determine how long that is possible:

• Larger sensors collect more total light during short exposures.
• Narrower field of view. A tighter lens concentrates pixels at the capture points, increasing usable detail where identification occurs.

These factors extend the range at which motion can be frozen. But even with large sensors, narrowed field of view, and optimized positioning, ambient light eventually falls below what physics allows for motion-free capture.

At that point, only two options remain, increase exposure time or switch to infrared illumination. Increasing exposure reintroduces blur. Adding infrared illumination preserves shutter speed. Only one protects evidence.

Cameras can use infrared illumination, invisible to people but efficient for sensors. Combined with monochrome capture, it delivers effective lighting and clearer motion detail while preserving the fast shutter speeds evidence requires.

Even when shutter speed and lighting are correct, detail can still be lost during the camera analog to digital conversion process. High resolution streams combined with high frame rates and complex moving backgrounds demand extremely high bitrates. These combinations can exceed encoder capacity and introduce visible detail loss, especially in identification areas. When encoder pipelines are stressed, macro-blocking, smearing, and quantization artifacts can erode the very details required for evidence.

To protect evidentiary quality during deployment:

• Reduce frame rate to 15 to 20 FPS.
• Define regions of interest and guarantee bitrate preservation in those regions.

By prioritizing bit rate where identification occurs, installers can achieve frame level clarity without overwhelming the encoder or wasting storage.

Frame integrity matters more than frame volume.

All UniFi cameras are designed for evidence capture. Form factor selection is about environment and durability, not image quality trade-offs.

Bullet & turret cameras:

• Predictable capture angles
• Lower maintenance
• No dome-related IR glare

Dome cameras:

• Greater vandal resistance
• More discreet appearance
• Require careful installation to avoid IR reflections

PTZ cameras:

• Ideal for patrol and situational awareness
• Should supplement, not replace, fixed evidence cameras

Primary evidence should always come from fixed cameras with known capture angles.

Supplementary cameras expand awareness, not evidence.

Effective deployments assign roles intentionally:

• Primary cameras: tight FOV, evidence-first
• Supplementary cameras: 180° / 360° for awareness
• PTZ: patrol and tracking

PTZ tracking can be triggered by primary cameras through Alarm Manager, extending coverage without sacrificing fixed evidence integrity.

Awareness and evidence serve different purposes and should not be conflated.

Evidence capture is not purely optical, it is behavioral. UniFi Pro cameras include visual detection cues, such as the animated detection ring, which:

• Draw attention during detection
• Encourage subjects to face the camera
• Improve capture angles naturally
• Can deter further malicious action