Page History

...

• a camera should be installed in a horizontal position (refer to manufacturer's documentation).

• character height is at least 15px, stroke width is at least 2px;
• minimum allowable contrast for uniformly contaminated license plates should be at least 10% (contrasting visibility of characters relative to the background is 25 on a 256-point scale);
• maximum allowable non-uniform contamination is no more than 12% (the ratio of the contaminated area to the total area of the license plate);
• the geometric proportions of the image shall not deviate by more than 10% from the real geometric proportions of the license plate.

...

For stable ANPR operation, make sure that the image of the license plate is not:

• unequally lit;
  Image RemovedImage Added
• overexposed;
  Image RemovedImage Added
• blurred;
  Image RemovedImage Added
• distorted;
  Image RemovedImage Added
• interlaced;
  Image RemovedImage Added
• dirty.
  Image RemovedImage Added

Some example number plate images that should be recognized fully and properly:

Image RemovedImage Added

The camera setup is described in detail in the recognition module manufacturer's documentation.

...