Every red light therapy device lists its wavelengths. Most buyers look at them the same way they look at processor specs on a laptop -- present, probably important, not fully understood.

The two most common numbers are 630nm and 850nm. They are not interchangeable. They do different things, at different depths, in different tissue.

What the number actually measures

Nanometres measure wavelength -- the distance between peaks of a light wave. In the visible and near-infrared spectrum, shorter wavelengths sit in the red range (around 620-700nm). Longer wavelengths push into near-infrared (700-1100nm), which the eye cannot see but tissue can absorb.

Penetration depth changes with wavelength. 630nm light is absorbed closer to the surface -- skin, superficial tissue, collagen layers. 850nm travels deeper, reaching muscle, joint tissue, and bone.

630nm -- the surface layer

At 630nm, research suggests the primary interaction is with mitochondria in surface cells. Some studies show this wavelength may support collagen synthesis, skin repair processes, and surface-level inflammation responses. The evidence base here is stronger than many people assume -- there are hundreds of published studies on red light and skin biology.

If your primary interest is skin texture, wound healing, or surface recovery, 630nm is where most of the studied mechanisms sit.

850nm -- going deeper

Near-infrared at 850nm penetrates several centimetres into tissue. This is the range most commonly used in studies examining muscle recovery, joint inflammation, and pain signalling. It may also cross the blood-brain barrier in sufficient doses -- which is why some researchers are examining it for cognitive and neurological applications.

If your interest is muscle recovery, joint support, or deeper tissue work, 850nm is the wavelength doing most of the relevant work.

Why most devices include both

A device that combines 630nm and 850nm covers both layers simultaneously. For whole-body panels and cap-style devices like the Lumina series, this dual-wavelength approach means you are not choosing between surface and depth -- you are addressing both in a single session.

The ratio of red to near-infrared varies by manufacturer and claimed use case. There is no universal optimal ratio in the literature yet -- this is an active area of research.

What this means practically

Before choosing a device, ask what you are actually trying to support. Surface-focused goals lean toward the 630nm range. Deeper tissue and recovery goals lean toward 850nm. Most general wellness and recovery devices include both.

Irradiance (power output, measured in mW/cm2) and distance from the device matter as much as wavelength. A high-irradiance 850nm device used at the correct distance will outperform a low-irradiance device at the same wavelength every time.

This article is for educational purposes. Red light therapy devices are not medical treatments. Consult a qualified healthcare provider before using any device if you have a medical condition.