Understanding IR Wavelengths for Security Lighting
850nm or 940nm Infrared Comparision
Human Visibility of Infrared Illumination
Both 850nm and 940nm are invisible to humans as illumination. The only difference is whether a faint red glow is emitted at the LED source when viewed directly. They do not brighten a scene or improve human vision in low light.
850nm IR illuminators may emit a faint red glow at the source when viewed directly. This glow is localized to the light source and does not illuminate the surrounding area. 940nm IR illuminators reduce or eliminate this visible emitter glow, but both wavelengths remain invisible as functional light to people.
For most security environments, the presence or absence of faint LED emitter glow has little practical impact on concealment, while wavelength choice significantly affects camera performance. For specialized deployments where any visible glow is undesirable, such as border surveillance, military operations, or correctional facilities 940nm IR is used.
The primary difference between 940nm & 850nm IR for covert use is the amount of red glow visible on the IR Illuminator.
IR Illuminators – Daylight
940nm IR Illuminators On – Night
850nm IR Illuminators On – Night
Note: The above “night/dark” images are recreations of what the human eye sees when looking at functioning IR Illuminators in complete darkness. Only the security camera can use the IR as “light”. AXTON’s 940nm IR illuminators have zero red glow. Other brands we tested have a reduced faint red glow when compared to 850nm.
Sensor Sensitivity and Image Performance for IR Wavelengths
Silicon CMOS and CCD camera sensors are most sensitive to infrared light in the 800nm to 900nm range, with a sharp drop in sensitivity beyond 850nm.
Infrared Sensitivity – Typical CMOS Sensor
NOTE: Chart for illustration only. Sensor response varies across sensor types and manufacturers. Most professional security cameras use standard CMOS sensors with similar infrared sensitivity profiles.
Choosing between 850nm and 940nm often comes down to performance versus concealment priorities. In most installations, 850nm offers superior camera sensitivity and range.
When to Use a 940nm IR Illuminator
940 nm infrared illuminators are designed specifically for fully covert surveillance, environments where the presence of any visible light, including a faint red glow at the LED source, must be avoided. This is their intended purpose.
| Application | Recommended Wavelength | Reason |
| Perimeter security | 850nm | Best range, brightness, efficiency |
| Parking lots / warehouses | 850nm | Standard surveillance with low power draw |
| Covert operations | 940nm | Required: zero visible glow |
| Military / tactical zones | 940nm | Discretion takes priority over image clarity |
| Prisons / corrections | 940nm | Fully covert fixtures needed |
| Railroad / Logistics | 940nm | Glow could be mistaken for a signal |
In applications such as military operations, border surveillance, law enforcement, and correctional facilities, concealment is critical. While some manufacturers market 940nm illuminators as “invisible,” many still emit a visible red glow, especially when viewed directly. This undermines their effectiveness for true covert use.
AXTON’s 940nm IR illuminators are fully covert, they emit no visible glow at the source, making them ideal for deployments requiring total stealth. For these niche but essential scenarios, 940nm remains a valuable option.
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Purchasing Information
AXTON Tactical 940nm IR Illuminators may be purchased through our website or, for possible lower pricing, from our distributors. See a list of AXTON distributors on our purchasing page. For large projects you may request a quote from us using the below button or contact one of our distributors.