The number of pixels captured for each license plate is more important than the distance to the target. In fact, many of our customers successfully capture license plates from almost a mile away. To increase pixels on target, adjust your camera’s zoom and resolution.
If your camera is capable of automatic optical zoom, or if you have a choice of lenses, it’s generally best to zoom the field of view to the area where the license plates will be captured. The screenshots below compare a camera with a wide field of view to a camera zoomed into the area of the license plates. Both approaches will work because the pixel width is sufficient in each shot; however, plate recognition will be more accurate in the zoomed example.
Adjusting your camera’s resolution can also increase the pixels for each plate. However, increasing the number of pixels will also increase the processing time. Therefore, if CPU resources are not infinite, increasing the resolution too much may decrease accuracy. We recommend setting the camera resolution no higher than 720p, making sure the plates still have enough pixels to be detected. If the camera is sufficiently zoomed, further decreasing the resolution may, counterintuitively, improve accuracy.
Our software reads USA plates wider than 75 pixels and European plates wider than 90 pixels. Pixel width beyond 250 pixels will not noticeably increase accuracy.