Red light vs near-infrared light

The simplest distinction is visibility. Red light sits at the long end of the visible spectrum, roughly 600–700 nm, and looks unmistakably red. Near-infrared begins just beyond that, commonly quoted from around 780 nm upwards, and is effectively invisible.

Why devices combine them

Different wavelengths behave differently when they meet skin — longer wavelengths generally travel further before being absorbed or scattered. Combining wavelengths is a design decision manufacturers make to address more than one depth at once.

A combined device is not automatically better than a single-wavelength one. It is a different specification, and what matters is whether that specification is appropriate for how you intend to use it.

A practical caution

Because near-infrared is invisible, you cannot judge whether it is working by looking at it. Some devices add a faint visible indicator LED for this reason. Never assume a dark panel is inactive — follow the eye-safety guidance supplied with the product.

Reading the numbers honestly

A wavelength figure like '633 nm' describes a peak, not a single pure output — real LEDs emit across a narrow band around that peak. Precise-sounding numbers are useful for comparison but should not be read as scientific guarantees of anything.

Where Ilumi publishes wavelength figures, they are the manufacturer's stated specifications for that exact product, shown on that product's page.