Use this calculator to determine if a number plate can be recognised over a given distance with a given lens.
For a number plate to be recognised an individual character MUST be a minimum of 20 pixels high in the captured image.
Ideally the recognition will be done with a resolution of 800x600 to minimise bandwidth and storage requirements.
Digital zoom should only be used to a maximum of 1.6x. The number plate is assumed to be 1m off the ground.