1. What Does “nm” Mean?
A nanometer is a unit used to measure the wavelength of light.
The wavelength tells us what type of light is being used:
- Around 630–660 nm falls within the visible red-light range.
- Around 810–850 nm falls within the near-infrared range.
- Near-infrared light is usually invisible to the human eye.
A higher wavelength number does not mean the device is stronger.
For example, 850 nm is not automatically more powerful than 660 nm. It is simply a different wavelength.
Wavelength describes the type of light—not how much light is being delivered.
2. Why Is 660 nm Commonly Used?
660 nm falls within the visible red-light range.
Because visible red light is generally absorbed and scattered more strongly in superficial tissues than near-infrared light, it is commonly used in skin-focused and surface-level PBM applications.
Common areas of research and product use include:
- Skin appearance
- Collagen-related processes
- Superficial tissue wellness
- Skin-focused recovery
- Surface-level cellular responses
A safe and accurate way to describe it is:
660 nm is a visible red wavelength commonly used for skin-focused and superficial tissue applications.
Avoid describing 660 nm as having one exact penetration depth. The amount of light that reaches the tissue varies according to the skin, tissue type, device intensity, treatment distance and exposure time.
3. Why Is 850 nm Commonly Used?
850 nm falls within the near-infrared range and is usually invisible to the human eye.
Near-infrared light generally has different absorption and scattering properties from visible red light. It may travel relatively deeper through certain tissues, which is why it is often used in body-focused applications.
Common uses include:
- Larger muscle areas
- Joint-focused devices
- Exercise recovery routines
- Wearable wraps
- Full-body panels
A suitable explanation is:
850 nm near-infrared light is commonly selected for applications intended to reach relatively deeper tissues than visible red light.
Some 850 nm LEDs may appear unlit or only faintly visible even when operating normally. This is because most of the emitted light is outside the visible range of the human eye.
4. Why Combine 660 nm and 850 nm?
Many devices combine 660 nm and 850 nm to provide both visible red light and near-infrared light in one treatment.
The purpose is to create broader coverage:
- 660 nm is commonly used for surface-focused applications.
- 850 nm is commonly used when relatively deeper exposure is desired.
This does not mean that combining both wavelengths automatically guarantees better results.
The overall outcome still depends on:
- Light intensity
- Treatment time
- Distance from the device
- Total dose
- Treatment area
- Device design
- Individual tissue characteristics
A balanced way to say this is:
Using both wavelengths may provide broader coverage, but the complete treatment protocol remains important.
5. Does Wavelength Alone Determine Results?
No.
Wavelength is important, but it is only one part of the treatment.
Two devices can both use 660 nm and still deliver very different experiences because they may differ in:
- Irradiance
- Treatment distance
- Session length
- Coverage area
- Light uniformity
- Total energy delivered
- Device construction
This is why a device should not be judged by wavelength alone.
No single wavelength is universally best. Wavelength, intensity, dose and treatment design work together.
