Almost every red light device lists two numbers. They are not decoration — they are the two ends of a real trade-off.
Red light works at the surface
Six hundred and thirty to six hundred and sixty nanometres. This is the visible red you can actually see, and it is absorbed largely in the skin and the tissue immediately beneath it.
That shallow absorption is not a limitation. It is the entire point when the target is thin tissue — the face, the eye contour, the skin itself. Send light deeper than the target and you have simply wasted it.
Near-infrared reaches further in
Eight hundred to eight hundred and fifty nanometres, invisible to the eye. The longer wavelength scatters less as it moves through tissue, so a greater share of the energy arrives at depth — muscle bellies, joint capsules, tendons.
This is why anything built around recovery leans on the infrared end of the range rather than the visible one.
Which is why most devices use both
Very little of the human body is a single depth. An ankle is skin, then tendon, then joint capsule. A lower back is skin, then fascia, then muscle.
Pairing the two wavelengths covers that stack instead of betting everything on one layer. A dual-wavelength device is the sensible default — unless you have a genuinely specific surface target, in which case a dedicated single wavelength does that one job better.
Wavelength is one variable of four. The other three decide whether it matters.
Irradiance. Distance. Time.
What a spec sheet cannot tell you
A device with immaculate wavelengths, used at the wrong distance for the wrong duration, delivers almost nothing. Wavelength decides where the light lands. Everything else decides how much of it gets there.
Photobiomodulation is an active research field, not a settled science. Published results vary, and so does study quality. PHŌRMA devices are wellness products, not medical devices, and nothing here is medical advice.