"Can I read plates with that camera?" is one of the most common questions on a site walk-through, and the honest answer is usually no — not with the camera watching the driveway or the car park. Treating plate capture as a bonus feature of an overview camera is how people end up with footage of a white ute and nothing more.
Why the overview camera cannot do it
An Australian standard plate is roughly 372mm wide. Reading the characters reliably takes somewhere around 150 to 200 pixels across that width — roughly 400 to 550 pixels per metre of scene, several times the density needed to identify a face.
A 4MP camera has 2,560 horizontal pixels, so at 500 pixels per metre it covers about five metres of scene. A camera watching a whole driveway covers fifteen or twenty, so each plate gets a fraction of the pixels it needs. Resolution is not the only problem:
- Angle. An overview camera sees vehicles obliquely, and characters compress as the angle increases.
- Exposure. A camera exposing for the whole scene blows a retroreflective plate under headlights or IR into a white rectangle.
- Shutter. General viewing uses slow shutter speeds at night, which smears a moving plate.
Each of those is a compromise. A plate camera stops compromising and optimises for one job.
The five things a plate camera needs
1. A dedicated camera. One camera, one lane, one capture point. The overview camera stays wide for context — the vehicle, its colour, how many people got out — and the plate camera does nothing else. They work as a pair, which is why the camera count tool treats them as separate positions.
2. A tight angle. Keep the camera within about 30 degrees of the vehicle's direction of travel, horizontally and vertically. Shallower is better. The ideal is a low mount — often 1.2 to 2 metres on a post or wall — looking almost straight down a lane at a vehicle approaching slowly. Mounted high over a wide gate, the geometry works against you.
3. A fast shutter. The setting most often missed. A plate on a vehicle moving at even 20km/h needs a short exposure to stay sharp — commonly around 1/500 of a second, faster again at higher speeds. Short exposures mean less light, which is why the next point matters.
4. Controlled lighting. Plates are retroreflective: they bounce light straight back at the source. With dedicated IR or white light near the camera axis, the plate lights up and the rest of the scene goes dark, which is exactly what you want. Without it, you are at the mercy of headlights, street lighting and sun angle. Many purpose-built plate cameras include their own illuminator and an exposure mode tuned for it.
5. A defined capture zone. Decide where the vehicle will be when the plate is captured — the boom, the gate line, a speed hump — and set the lens, focus and exposure for that distance. Plate cameras work at a spot, not across an area, and a longer lens from further back often beats a wide lens up close because the angle is shallower.
Distance, lens and lane width
Decide the capture point, measure the distance, then pick the lens that makes the scene there about two to three metres wide — wide enough for a vehicle that is not perfectly positioned, narrow enough to keep pixel density high.
- Single lane, 6 to 10 metres — often a 6 to 12mm lens.
- Longer approach, 15 to 25 metres — a longer varifocal, commonly 12 to 50mm, with focus and alignment becoming fussier.
- Two lanes — two cameras. One straddling both lanes halves the pixels per plate and worsens the angle on at least one.
Varifocal is worth paying for here. Getting it right is iterative: adjust, drive a vehicle past, review the capture, adjust again.
Realistic expectations
Being straight about the limits is more useful than a specification sheet.
- At low speed, with the right setup, results are good. A vehicle rolling through a gate at 10 to 20km/h, lit by a dedicated illuminator, on a shallow angle: expect to read most plates most of the time.
- At road speed it gets much harder. Highway-speed capture is the domain of purpose-built enforcement equipment. On a business site, slow the vehicles down — a speed hump improves capture more than any camera upgrade.
- At night, lighting decides everything. With a dedicated illuminator, night capture can be cleaner than daylight because the plate is the brightest thing in frame. On ambient light alone, expect poor results.
- Dirty, damaged or obscured plates will not read. Nor will one behind a bull bar, bike rack, trailer or tinted cover. This is common.
- Rain, fog and low sun degrade capture. Direct sun into the lens at dawn or dusk can blind a camera for twenty minutes a day, every day.
- Motorcycles are harder. Smaller plates, mounted at an angle, usually only visible from behind.
Reading plates versus recognising them
Two outcomes are worth separating. Human-readable capture means a person reviewing footage can read the plate. For most businesses that is the real requirement: something happened, you want the plate, you find it in the footage.
Automatic recognition (ANPR or LPR) means software turns the plate into text, so you can search for a vehicle, keep a list of known vehicles, or trigger a gate. It needs everything above plus consistent conditions, and it will make errors — characters confused, plates missed. Treat a recognised plate as a strong suggestion to confirm by eye. If a decision matters, look at the image.
Our platform logs vehicle events and counts and keeps short clips around each one, so a plate capture sits in the timeline for that gate. That makes the right frames easy to find; a person still reads the plate and decides what it means.
Before you commit
- Stand at the capture point. Is there a mounting position on a shallow angle at a sensible height?
- Can vehicles be slowed there?
- Is there power and a cable path within the 100-metre limit on copper runs?
- What happens at the worst time of day for sun angle?
- Who will use the captures, and for what — incident review, deliveries, or access control?
A plate camera that only works on sunny afternoons is a common and avoidable outcome. To have one specified against your actual gate geometry, ask for a quote. The resolution and lens guide covers the pixel maths, and the glossary explains the terms.