LPR camera

[Co78 0]

I started a project with a friend to install a few security cameras at the subdivision entry/exit point. We wanted to have a high resolution camera so we purchased a Reolink 811A 4K camera. We noticed that during the day getting the plates is a hit or miss depending on the speed of the cars. At night things get worse as the camera gets overwhelmed by the tailgate lights. Even with the IR of the camera off and in B&W mode, and using a separate IR illuminator the plates are not visible. 

I know there are specialized LPR ip cams but we thought that a 4K camera would work better than a 2 MP one. Are there any suggestions as how we can improve the readability during the night? If we decide to use a different camera, what should we look for as far as specs? Is there necessary to have an IR light even with a LPR camera? If yes, what is the best location relative to the camera itself?

I really appreciate any suggestions or education you can offer. Thank you. 

[Mark_M 3]

On 9/14/2023 at 3:18 AM, Co78 said:

I know there are specialized LPR ip cams but we thought that a 4K camera would work better than a 2 MP one. Are there any suggestions as how we can improve the readability during the night? If we decide to use a different camera, what should we look for as far as specs? Is there necessary to have an IR light even with a LPR camera? If yes, what is the best location relative to the camera itself?

I really appreciate any suggestions or education you can offer. Thank you. 

What makes an LPC/LPR camera:

• High noise to signal ratio (often said in dB).
• Large focal length (zoom level).
• Large imaging sensor - suitable size for the resolution.
• High exposure speed (not necessarily higher FPS).

Reolink use cheap quality imaging sensors and cheap quality processors. Here's why:

Generally an LPC/LPR camera is 2MP or 4MP. Imaging sensor size matters for light sensitivity on each pixel cell.

A general guide: 2MP, use an imaging sensor that is 1/2.8" or larger. At 4MP, an imaging sensor 1/1.8" or larger.

For 8MP (you won't use this for LPC/LPR), the sensor should be 1/1.2" or larger. Reolink manufacture a 12MP camera at 1/2.49".... this is an absolute joke of how Reolink use the cheapest quality possible.

 

Why does the cmos sensor size matter?

A larger surface area for the imaging sensor can collect more photons of light in a shorter period of time. This means the exposure time can be lower. Lower exposure time means fast moving objects are less of a blur.

Reolink and other consumer brands suffer because they use a cheap imaging sensor and to compensate the exposure speed has to be longer.

 

Why lower resolution and more zoom?

Optical zoom is far more effective than increasing the resolution. Lower resolution also means less processing power is needed for HLC (High-light compensation) or WDR (Wide dynamic range) so that the headlights and taillights do not blow out the image. Lower image resolution also helps LPR software to recognise the plate in OCR (optical character recognition) because less processing power is needed.

IR light is needed for LPC/LPR, this is to illuminate the plate so it appears brighter than light from the headlights/taillights.