The principles, effective distance and common misunderstandings of infrared night vision
Explain how infrared fill light works, the gap between nominal distance and actual effect, and how to deal with common problems such as reflection, occlusion, and attenuation.
How it works
The built-in infrared LED of the camera emits 850nm (or 940nm) infrared light invisible to the human eye, which is reflected back after hitting the object. The image is received by the sensor. Nighttime images usually automatically switch to black and white because color information has no practical value at this time. Turning off the color filter (ICR switch) increases the amount of light entering.
Nominal distance vs actual distance
The "infrared 50 meters" marked by the manufacturer usually refers to the limit value under the ideal experimental environment (open, unobstructed, high target reflectivity). In actual projects, it is recommended to estimate the available distance based on 60% to 70% of the nominal value.
| Infrared light configuration | Nominal distance | Engineering available distance |
|---|---|---|
| Single lamp / 4 dot matrix | 20～30 meters | 12～20 meters |
| 6～8 dots | 30～50 meters | 20～35 meters |
| High power array | 50～80 meters | 35～55 meters |
| Laser fill light | 100～300 meters | Requires telephoto lens |
Frequently asked questions and solutions
- The picture is white/overexposed: There are strong reflectors such as walls and columns at close range. Turn on smart infrared or reduce the infrared intensity.
- Darkness on all sides (vignetting): The focal length of the lens does not match the angle of the infrared light (such as a telephoto camera with a wide-angle light), and a matching model needs to be replaced.
- Highlights with spider webs/dust: Infrared light is reflected by suspended objects at close range, cleaning the shield and lens.
- Photographing white through glass: Infrared is reflected back to the lens by the glass. You should move away from the glass or stick to the glass and turn off infrared.
- The more it is used, the darker it gets: Infrared lights are attenuated, and high-temperature environments that are turned on for a long time will accelerate aging. Pay attention to heat dissipation and stable power supply.
Installation suggestions
- Avoid the infrared radiation of two cameras, which will interfere with each other.
- There should be no close obstructions such as branches or billboards within the infrared radiation range.
- When it is necessary to conceal or avoid red storms, you can choose 940nm or black light (no red storm) models.
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