Set a red light therapy panel 8–50 cm from your skin: closer for a small area such as your face, further away to cover a larger area. Sessions last 10–30 minutes, at most 30 minutes a day on the same area. Smart Series panels measure 132–152 mW/cm² at 15 cm.
Why does distance change the light that reaches you?
A panel's light spreads out as it travels. Further away, the same light is shared by a larger area, so less of it reaches each square centimetre of skin: irradiance, measured in mW/cm², falls as the distance grows. Close to a large panel it falls more gently than further away, so there's no single conversion factor between distances, and an irradiance figure only means something next to the distance it was measured at. Our article on what irradiance means explains the unit.
That's why measured figures matter. A 2016 review of 74 light-therapy studies found that 73% didn't say how the light was measured and relied on the manufacturer's stated values (Hadis et al.). Our figures are spectrometer readings at 15 cm: besides the Smart Series value above, the Pro Series panels for professional use measure 119 mW/cm² (Beauty Pro) and 122 mW/cm² (Fitness Pro). We don't estimate values for other distances.
Should you sit closer or further away?
It depends on the area you want to light. Each LED in a Smart Series panel has a 30° beam, so the light fans out as it travels: further from the panel, the beams overlap and the lit area grows; closer, the light stays concentrated on a smaller patch.
So sit closer for a small area such as your face or neck, and step back within the range when you want to cover a larger area such as your back or legs in one session. Researchers count this lit area as a setting of its own: a 2011 reporting guide lists the beam area at the skin, which isn't necessarily the size of the light source, among the parameters every study should state (Jenkins & Carroll).
Panel size does the same job as distance. The Smart Small covers the face, neck and shoulders from a table stand; the Smart Medium, twice as tall, also reaches the back or legs, on a floor stand or wall mount. You can compare them in our panel collection. Both are made by a partner manufacturer to RedLightMed's specification and European (CE) requirements, and every unit is checked in Hungary.
Is closer always better?
No. More light isn't automatically better. Research explores a biphasic dose response: a 2009 review describes cell and animal experiments in which lower amounts of light often showed better results than higher ones (Huang et al.). So there's no prize for sitting as close as possible: choose a distance within the range that covers the area you want, and stay with it.
Time and distance work together, so change one at a time. If you move closer or further away, keep the session length the same until you've settled on your distance. How long and how often to use the panel is covered in how often to use red light therapy.
Does distance decide how deep the light goes?
Not mainly. How deep light travels into the skin depends above all on its wavelength: in a 2017 computer model of light passing through the layers of the skin, penetration depth increased with wavelength (Ash et al.). Smart Series panels have two separately controlled channels: red (610, 630 and 660 nm) reaches the layers near the surface, near-infrared (810, 830 and 850 nm) reaches deeper layers.
Distance decides how much light arrives at your skin and over what area; the wavelength decides how deep it can travel. Our article on how red light therapy works explains more.
How do you measure and keep your distance?
Measure from the front of the panel, where the LEDs are, to the skin you want to light, not from the stand or the wall. A tape measure is enough.
Keep the panel parallel to that area, so all of it sits at about the same distance. Then make the setup repeatable: mark where your chair or feet go, or note the height of the stand, so every session starts from the same spot.
Protect your eyes. Close your eyes or wear the goggles; there's a pair in every box. Our article on whether red light therapy is safe for your eyes goes into more detail.
It isn't recommended for children under 12, while breastfeeding, with epilepsy, with known tumours or metastases, or if you're sensitive to light. During pregnancy, only after talking to your doctor.
Sources
Hadis MA, Zainal SA, Holder MJ, et al. The dark art of light measurement: accurate radiometry for low-level light therapy. Lasers Med Sci, 2016. PubMed 26964800
Jenkins PA, Carroll JD. How to report low-level laser therapy (LLLT)/photomedicine dose and beam parameters in clinical and laboratory studies. Photomed Laser Surg, 2011. PubMed 22107486
Huang YY, Chen AC, Carroll JD, Hamblin MR. Biphasic dose response in low level light therapy. Dose Response, 2009. PubMed 20011653
Ash C, Dubec M, Donne K, Bashford T. Effect of wavelength and beam width on penetration in light-tissue interaction using computational methods. Lasers Med Sci, 2017. PubMed 28900751
