ANPR Camera Setup Best Practices

Ensure Sufficient Plate Pixel Density

For reliable recognition, the license plate must occupy enough pixels in the frame. As a general guideline, the minimum recommended resolution is approximately 120 pixels across the plate width, while the optimal range is between 150 and 250 pixels across the plate width for best results. If the plate appears very small in the image, recognition accuracy will be poor.

Example: Plate Pixel Density

Poor setup - Camera too wide:

In this scenario the camera covers too large an area, causing plates to occupy too few pixels.

Good setup - Camera zoomed to capture lane:

Here the camera is focused on a single lane and the plate occupies a much larger portion of the frame.

Keep the Horizontal Angle Low

ANPR works best when the vehicle approaches the camera as directly as possible. Large horizontal angles cause plate distortion and reduce recognition accuracy. The recommended horizontal angle is ideally less than 30°, with best performance achieved when the angle is under 20°.

Example: Horizontal Angle

Poor setup - Steep viewing angle:

Plates appear skewed and harder to read.

Good setup - Camera facing vehicle path:

Plates are captured front-on with minimal distortion.

Keep the Vertical Angle Low

The vertical angle between the camera and the plate should also be minimised. Mounting cameras too high results in steep vertical viewing angles, which can obscure characters. The recommended vertical angle is ideally less than 30°, with best performance achieved when the angle is under 20°.

Example: Vertical Angle

Poor setup - Camera mounted very high:

Plates appear compressed and difficult to read.

Good setup - Moderate mounting height:

Plates remain flat and clearly visible.

Limit the Field of View

ANPR cameras perform best when monitoring a single lane or narrow area.

Attempting to monitor multiple lanes often results in:

• Plates that are too small.
• Higher recognition error rates.
• Increased false detections.

As a best practice, configure one ANPR camera per lane where possible and use zoom to focus on the target detection area.

Example: Lane Coverage

Poor setup - Camera covering 4 lanes:

Recommended setup - Camera covering 1 lane:

Avoid Motion Blur

Fast-moving vehicles combined with slow shutter speeds can cause motion blur, making plates unreadable.

Ensure that:

• The camera supports ANPR or traffic mode.
• Shutter speed is high enough.
• IR illumination is available for night conditions.

Ensure Good Lighting Conditions

Lighting has a significant impact on ANPR accuracy.

Key recommendations include avoiding direct sunlight into the camera, preventing headlight glare at night, using cameras with IR illumination where possible, and ensuring that license plates are evenly illuminated.