So on this picture you get a nice view of the front of the store and the cars and even when you zoom in you may not be able to read a plate so this article will help you understand some of the factors you will need in order to view license plates with your cameras.
Contact Larry Love at Peak Alarm for more information or if any corrections need to be made to this blog. (801) 428 1384 Larry@peakalarm.com http://www.peakalarm.com
DISTANCE TO THE CAR – Using a lens calculator we can determine how wide a view you will need and the lens
LIGHTING – IR LED system on your cameras (check the rating- often it will say 30 feet but will only work at about 20′)
ANGLE OF CAMERA(S) and how high the camera is mounted – If the camera is mounted high on the building and the cars drive into the driveway on an angle or in a dip this could cause issues
MP RESOLUTION OF YOUR CAMERAS (2MP, 4MP or 4K cameras are all great cameras, understand that the higher the MP the more storage they use)
LENS ON THE CAMERA – most cameras are fixed at 2.8 or 3.6mm and some are verifocal 2.7-12mm and other more expensive cameras have higher mm adjustment capability.
HOW FAST IS THE CAR GOING
There are other factors but for this article I will keep it simple
IMPORTANT INFORMATION YOU NEED TO KNOW:
I have a customer that wants to see plate numbers 120 feet from his building at the driveway entrances. Lighting and the proper choice of camera is essential.
Using a 2MP High Definition camera you will need a 28mm lens on your camera at 120 feet and your camera view will be 22 feet across and 12 feet high and you will get 85 pixels per square foot.
If you don’t have the right IR and lighting then it may be difficult at night to see plates. Using a 4MP camera would require a 13mm lens to see 44 feet across to view a plate. Keep in mind that you are not guaranteed to see plate numbers even when you use the right lens and do the calculations properly since most cameras are not license plate cameras. We can install actual license plate cameras that are made for this purpose and then you have a much better chance of seeing plate numbers. In the above situation it would be much better to move the cameras closer to the cars and move the camera down on a pole looking directly at the plates rather than mounting the cameras on a building at 13 feet in the air.
You will need a minimum of 60 pixels per square foot to view a plate number and it would be much better at 100.
Purpose Min. Required px/ft
Detect activity 8
Observe behavior 16
Recognize person 30
Identify person 60
Read license plate 60
Identify USD 150
Read 10pt text 1200
Most cameras from big box stores now are fixed lens cameras at 2.8 or 3.6mm giving you a very wide view. Using them in residential application is ok but looking 120 feet away would give you a view of 80 feet across and 60 feet high so you would not be able to see a plate number.
My cameras at my home are 500 TVL and 700 TVL or 700,000 lines and the newer 2.1MP cameras are 3 times the resolution so your chance to see plate numbers is better with a 2MP or 4MP camera but there are other factors.
With the understanding of the different factors please know that a $30 or $50 dollar camera is not going to cut it. Hikvision has a great camera that starts at $850 and the Q Series AXIS camera starts at $1,850 for the camera, you would then need to purchase the NVR that has the ability to log plate numbers. We have less expensive cameras that very well could see plate numbers that are much closer to the home or business and it also depends on how fast the cars are going as to which cameras you decide on.
Understand that you can purchase cameras just for reading plate numbers and the NVR recorders have the ability to log those plate numbers and you can actually buy a list of plate numbers that your system can compare the data to in order to determine if a stolen car is in your area or lot or if they are behind on their car payments. Some tow companies use these programs to repossess cars.