Last updated: June 2026
Capturing a readable number plate from a moving vehicle is one of the most technically demanding tasks for a CCTV camera. The shutter speed determines whether the plate appears as a readable image or a blurry streak. UK speed limits, typical vehicle approach speeds, and the angle of the camera relative to the road all affect the shutter speed required. The common mistake is using the default shutter speed (typically 1/25 or 1/50 second for PAL cameras), which produces motion blur on any vehicle moving faster than walking pace.
The Relationship Between Shutter Speed and Motion Blur
A vehicle travelling at 30 mph (13.4 metres per second) moves 0.54 metres during a 1/25 second exposure. At a 10-metre distance from the camera, the plate moves approximately 3–5 pixels during the exposure depending on the camera resolution and focal length. Motion blur of 3–5 pixels makes the plate characters unreadable. At 1/500 second, the vehicle moves only 27 mm during the exposure, producing less than 1 pixel of blur. The formula is: maximum acceptable shutter speed (seconds) = 1 / (vehicle speed in m/s / target pixel tolerance). For reliable number plate reading at 30 mph, a minimum shutter speed of 1/500 second is required. For 60 mph motorway coverage, 1/1000 second or faster is needed.
The Light Sensitivity Trade-Off
A faster shutter speed reduces the amount of light reaching the sensor by the same proportion. A 1/500 second exposure lets in 20 times less light than the default 1/25 second. The camera must compensate with: higher gain (ISO), which introduces noise that may make the plate unreadable; wider aperture (lower f-stop), which reduces depth of field (the plate may be in focus but the vehicle body may not); or supplementary IR illumination at the plate position. For reliable number plate capture at night, dedicated IR illuminators directed at the plate position are essential. The camera’s built-in IR is rarely sufficient for the shutter speeds needed to freeze vehicle motion at night.
Optimal Shutter Speed by Scenario
For a driveway or private road where vehicles approach at walking speed (5–10 mph), 1/120–1/250 second is sufficient. For a residential street where vehicles travel at 20–30 mph, 1/500–1/1000 second is required. For a main road at 40–60 mph, 1/1000–1/2000 second. For ANPR cameras dedicated to number plate reading, the fastest shutter speed the lighting conditions allow should be used, typically 1/1000–1/4000 second. The exposure should be fixed (not automatic) to maintain consistent shutter speed regardless of scene brightness changes, which can cause automatic exposure to slow the shutter speed at the critical moment a vehicle enters the frame.
Configuration Recommendations for UK Installations
For cameras intended to read number plates, use the camera’s manual exposure mode and set a fixed shutter speed of 1/500 second minimum for daytime and 1/250 second minimum for night-time (with adequate supplementary IR). Enable the camera’s highlight compensation feature to prevent the plate from overexposing (glowing white). Position the camera so the plate is at an angle of 15–30 degrees from perpendicular — this reduces headlight glare reflection from the plate surface. For dedicated ANPR installations, use a camera with a 1/1.8 sensor or larger, which provides better low-light performance at fast shutter speeds than the smaller 1/2.7 or 1/3 sensors found in general-purpose cameras.
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Frequently Asked Questions
1. What shutter speed do I need to read a number plate?
Answer: For a vehicle at 30 mph, 1/500 second minimum. For 60 mph, 1/1000 second minimum. For walking speed (5–10 mph), 1/120–1/250 second is sufficient. For more detail, see Future of Pubs, Bars and Restaurants CCTV in 2026 - UK trends and technology. Also read our related guide: Camera MAC Address Security: Spoofing Risks. Browse our comprehensive CCTV knowledge base at CCTV Systems Guide. Official UK guidance on this topic: GOV.UK.
2. Why is my number plate blurred in CCTV footage?
Answer: The default shutter speed on most cameras (1/25 or 1/50 second) is too slow to freeze vehicle motion. The plate moves 3–5 pixels during the exposure, creating blur that makes characters unreadable. For more detail, see Future of Home WiFi CCTV in 2026 - UK trends and technology. Also read our related guide: SNMP for CCTV Camera Monitoring: Uptime and Bandwidth.
3. Does higher shutter speed work at night for number plates?
Answer: Only with adequate supplementary IR illumination directed at the plate position. The camera’s built-in IR is rarely sufficient. A 1/500 second exposure at night requires 20x more light than the default 1/25 second. For more detail, see Can you record footage from public car parks without visible signage? UK Car Parks CCTV rules explained 2026. Also read our related guide: VLAN for Camera Isolation: Network Security Best Practice.
4. What angle is best for number plate capture?
Answer: 15–30 degrees from perpendicular to the plate surface. This angle reduces headlight glare reflection. 0 degrees (straight on) reflects headlights into the camera, overexposing the plate. For more detail, see How to install CCTV for Construction Sites - UK step by step guide 2026. Also read our related guide: Multicast vs Unicast for Multi-Viewer CCTV Setups.
5. Do I need a special camera for number plate reading?
Answer: Dedicated ANPR cameras with larger sensors (1/1.8 or larger), faster shutter speeds, and external IR illuminators are recommended for reliable number plate reading. General-purpose CCTV cameras can read plates in good lighting but struggle at night. Also read our related guide: PoE Power Budget Calculation: Real vs Rated.
Conclusion
The difference between a security system that works and one that frustrates is understanding the real-world behaviour of cameras, cables, and the environment they operate in. Manufacturers sell specifications. Installers solve problems. The questions above represent the issues that UK homeowners and businesses actually face — the ones the spec sheets do not mention.
Article by Gary Pearce, qualified security systems engineer. For a free security assessment, visit gary-pearce-home-services.pages.dev. This guide was last updated June 2026. Verify current UK regulations with the ICO.