Wavelengths in red light and infrared: what those nanometres mean
In short
Nanometres on a product page say nothing about quality, but they do tell you what a device does. Here is how to read them.
- Near infrared is light, far infrared is warmth
- 660 and 850 nm are the best researched
- A higher number is not more powerful
- Distance and time count for more than an extra colour
Near infrared, far infrared, 660 nm, 850 nm, FIR: when you compare a red light panel or an infrared sauna blanket, within two product pages you come across a row of numbers nobody ever explained to you. This guide explains what those nanometres mean, without a physics textbook and without foggy marketing language.
You'll read what a wavelength is, how the spectrum from visible red light to far infrared fits together, why 660 and 850 nanometres of all numbers turn up everywhere, and why a higher number is not automatically better. And you'll learn what to look out for when a seller uses big words about wavelengths. If you want the bigger picture first, start with the guide to red light therapy. Here we get into the technology.
What is a wavelength, actually?
Light and infrared are both electromagnetic radiation. You can picture that radiation as a wave, just like waves on water. The distance between two wave crests is the wavelength. With water you measure it in metres, with light in billionths of a metre.
That wavelength determines almost everything you notice about radiation. Short waves you see as blue, slightly longer ones as green, longer still as red. If the wave gets even longer, your eye stops seeing it and we call it infrared. Go the other way, shorter than violet, and you end up at ultraviolet. So it is one continuous range that we have stuck names on, not a collection of separate kinds of radiation.
That is straight away the most important thing to remember from this guide: colour, warmth and invisible infrared are not different things, but the same phenomenon at a different wavelength.
Why it's measured in nanometres
A nanometre, abbreviated nm, is a billionth of a metre. That is an absurdly small number, but it does keep the table readable: visible light runs from about 380 to 780 nm, and you don't have to write down decimals with eight zeros.
With far infrared the numbers get so big that nanometres become awkward. There people switch to micrometres, abbreviated µm. One micrometre is a thousand nanometres. So if you see 850 nm on one product page and 9 µm on another, you are comparing 850 nanometres with 9000 nanometres. That is a difference of a factor of ten, and it is exactly the difference between light that goes into your skin and warmth you feel on your skin.
The spectrum from red light to far infrared
Below is the classification used in most technical documentation. The boundaries are conventions, not laws of nature: different fields draw the line between near, mid and far infrared slightly differently. In the sauna world, for example, you often only hear the split between near and far, while the official classification has three.
| Range | Wavelength | What it is | Where you come across it |
|---|---|---|---|
| Visible light | about 380 to 780 nm | everything your eye sees as colour, from violet to deep red | lamps, screens, the blue and green settings of an LED panel |
| Red light | about 620 to 780 nm | the last stretch of visible light before infrared begins | red light panels and LED masks, usually around 630 and 660 nm |
| Near infrared (IR-A) | 780 to 1400 nm | invisible, but otherwise still behaves like light | red light panels and infrared lamps, usually around 810, 850 and 940 nm |
| Mid infrared (IR-B) | 1400 to 3000 nm | is mainly absorbed in the top layers of the skin and feels warm | part of the spectrum of glowing heat lamps |
| Far infrared (IR-C) | 3000 nm to 1 mm, so 3 µm and above | radiant heat, you feel it as warmth straight away | infrared sauna blankets, infrared cabins, heating panels |
Two things stand out. First, red light and near infrared are close together: 660 and 850 nm differ by less than a factor of two. Second, far infrared is miles away from them. A sauna blanket and a red light panel are sold in the same webshop, but they work in completely different parts of the spectrum. That difference is covered in more detail in the article on red light and infrared and what the difference is. Anyone looking for a sauna blanket with red light therapy runs into exactly that gap.
Near infrared and far infrared: the difference that really matters
The terms near infrared and far infrared are used interchangeably as if they were flavours. They are not. They differ in what happens to the radiation as soon as it reaches your skin.
Near infrared: light that goes in
Near infrared sits right next to red light and behaves accordingly. It is invisible, but it is not swallowed up by the surface straight away. In the range from roughly red to some way into the near infrared, radiation is absorbed relatively little by water and blood, so those wavelengths penetrate further into tissue than blue or green light. That is why this part of the spectrum is often called the optical window in the literature.
Important: that does not mean heat is produced. A good red light panel hardly feels warm. What exactly happens to that light in the tissue and what the research shows about it is explained in the Luxyor knowledge base. You deliberately won't find penetration depths in millimetres here, because those numbers differ per tissue, per person and per measuring method, and adverts routinely make them look better than they are. Where the often quoted figure of five centimetres comes from and how deep infrared really penetrates the skin has been worked out point by point elsewhere.
Far infrared: warmth you feel
Far infrared, the FIR in many product descriptions, lies well beyond near infrared. These wavelengths are almost completely absorbed in the outer layers of the skin. There they turn into heat, and that heat spreads further through your blood and tissue, just like with a warm bath or a hot water bottle.
That is also why a sauna blanket uses far infrared. Every surface that is warmer than its surroundings emits infrared, and the warmer it is, the shorter the wavelength of that radiation. A heating element of a few tens of degrees has its peak somewhere around eight to ten micrometres. That is not the manufacturer's choice but simple physics: that wavelength belongs to that temperature. How this is done in a blanket is explained in the article on how an infrared sauna blanket works and what FIR heat is.
If you want to see the two side by side, the article far infrared versus near infrared goes into it in more depth.
If a device feels nice and warm, it almost certainly works with far infrared or ordinary radiant heat. If you hardly feel any warmth while there is bright red light, you are in the range of red and near infrared. What your skin feels gives away which part of the spectrum you are in.
Why 660 nm and 850 nm are mentioned so often
Open ten product pages for red light panels and nine times you'll see 660 and 850 nm. That is no coincidence and not an agreement between manufacturers either. These two values are used most often in scientific research on red light and near infrared, so most is known about exactly these wavelengths. Manufacturers follow that, because ordering an LED close to the studied value makes more sense than coming up with something yourself.
660 nm is deep red and just visible. 850 nm is near infrared and you can barely see it. Many panels have both, so you get both the visible red part and the invisible part. What that does and what the research does and does not say about it, we deliberately keep out of this technical piece. For that we refer you to the knowledge base, where the evidence is set out per topic.
What a nanometre value actually is
An LED does not emit one single, perfect wavelength but a narrow band around it. The value a manufacturer states is the peak or the middle of that band. If it says 660 nm, in practice light also comes out just below and just above that value. That is normal and not a sign of a bad product. It does mean you shouldn't overrate a difference of a few nanometres between two panels.
What the seven wavelengths of the Lumi panels mean
The Luxyor Lumi 110 and Lumi 700 are sold as panels with seven wavelengths. The product information states what that means in concrete terms, and that is exactly what you'll find below. No more, because anything beyond the manufacturer's specification would be guesswork.
| What the product information states | What it says | What that means |
|---|---|---|
| Number of wavelengths | seven, combined in one panel | several LED colours side by side in the same grid |
| Range | 480 to 940 nm | from blue green visible light into the near infrared |
| Emphasis | 660 nm red and 850 nm near infrared | the two values that appear most often in research |
| Visible part | everything below about 780 nm | you see it shine, from the blue green end to deep red |
| Invisible part | the near infrared up to 940 nm | you don't see it, or at most as a faint glow |
| Warmth | no heat output | this is light, not a heat source like a sauna blanket |
Note that the individual values of all seven wavelengths are not in the product description. Only the outer limits and the two most important ones are mentioned. If you want to know exactly which seven values are in your unit, check the manual or ask customer service. That is also a good test for any seller: a shop that can simply tell you this knows what it is selling.
The lower limit of 480 nm is in the blue green part of visible light. So that is not infrared and not ultraviolet either. Ultraviolet only starts below 380 nm and is not in these panels. That is an important distinction, because UV is the part of the spectrum that can cause burning, and that does not occur here.
- Seven wavelengths from 480 to 940 nm, with emphasis on 660 and 850 nm
- Panel 91 cm tall with 300 LEDs, free standing or wall mounted
- Adjustable via touchscreen or remote control, with adjustable intensity
- 60 days to change your mind and a 2 year warranty
Why a blanket, a lamp and a panel use different wavelengths
Once you know the spectrum, the product range suddenly falls neatly into place. Each type of device sits in a different part of it, and that explains why they feel so different.
| Device | Mainly works with | What you notice | What it is usually used for |
|---|---|---|---|
| Infrared sauna blanket | far infrared, in micrometres | clear warmth over your whole body, you start to sweat | warming up, a moment of rest, relaxing after a long day |
| Red light panel | red light and near infrared, 480 to 940 nm | bright red light, hardly any warmth | targeted light on one part of the body or the skin |
| Infrared lamp | a broad mix, with emphasis on near and mid infrared | targeted, often strong warmth in one spot | keeping a shoulder, back or knee warm |
| LED mask | red light, sometimes blue and near infrared | light right on the skin, no warmth to speak of | the face, with fixed short sessions |
Notice that the column with what you notice follows almost entirely from the column with wavelengths. A blanket makes warmth because far infrared turns into heat in the skin. A panel feels cool because it works in the optical window. Help with choosing between these types is in the guide to buying a red light lamp or panel.
What your eye can and cannot see of these wavelengths
In practice this causes the most confusion, so here it is short and concrete.
- Around 480 nm you see blue green light. Bright and clearly there.
- Around 630 to 660 nm you see deep red. This is the light that turns the whole room red.
- Around 780 nm seeing more or less stops. The boundary is not sharp and differs from person to person.
- Around 850 nm you see at most a faint, dull glow if you look straight into it. Many people then think those LEDs are broken.
- Around 940 nm you generally see nothing at all.
- You never see far infrared from a sauna blanket. There is no red glow, because the wavelength lies thousands of nanometres beyond visible.
So you can't conclude anything from invisibility. A sauna blanket that gives off no red light is not broken, and a near infrared LED that barely glows is simply doing its job. The reverse is also true: a lot of red light says nothing about how much invisible near infrared comes with it.
Is a higher wavelength better?
No, and this is the most persistent misunderstanding around this topic. A wavelength is a property, not a performance figure. 940 nm is not stronger than 660 nm, just as green is not better than blue. They do something different.
In fact, going on to ever higher numbers reverses at some point. Beyond the optical window, water in your tissue absorbs the radiation better and better, so the energy stays in the top layers and turns into heat there. That is exactly what far infrared does. More wavelength therefore does not mean deeper there, but actually more superficial and warmer.
A wavelength tells you what kind of radiation you get, not how much or how good.
What does say something about how much you get is the amount of radiation that lands on your skin per unit of area, and how long you stay under the device. Two panels with identical wavelengths can differ considerably in that respect, depending on the number of LEDs, the power, the build and the distance you sit at. Choosing a wavelength is therefore step one, not the whole choice.
What several wavelengths in one panel mean in practice
Panels with seven wavelengths sound impressive, and it is no small thing, but it is useful to know what you actually get out of it in practice.
The advantage is real: one device covers both the visible red part and the near infrared, and you can choose a different programme for each goal without buying a second device. For most people at home, that is more convenient than a panel with one fixed colour.
The nuance belongs here too. The total power is divided across those LEDs, so seven wavelengths does not mean seven times as much of everything. And the two values that most is known about are still 660 and 850 nm. The extra colours are an addition, not a replacement for them. A seller who suggests that every extra number makes the device a level better is mostly selling you a list.
If you're choosing between two panels, first compare the size and the distance you need to sit at, and only then the number of wavelengths. A larger panel that covers your whole back makes more difference in practice than one extra LED colour.
Wavelength is only part of the story
If you only look at nanometres, you miss the factors that matter at least as much. These belong on the list in any case:
- Distance. Radiation drops off quickly the further away you are. Thirty centimetres more changes a session more than a different wavelength.
- Surface area. A small panel on a large back simply lights less of your body, however good the LEDs are.
- Time. How long and how often you use a device has nothing to do with the spectrum. Guidelines for that are in the guide on how often and how long to use an infrared blanket.
- Power and build. The number of LEDs, their quality and the way the panel gets rid of the heat from the LEDs themselves determine what is left of it after a year.
- Keeping it up. The device in a handy spot gets used. The perfect device in the meter cupboard does not.
How to judge what a seller says about wavelengths
You don't need to be a physicist to recognise nonsense. Go through these steps on a product page.
- Look up the numbers yourselfAre there concrete values in nanometres, or only words like medical, professional or highest quality? No numbers is a signal in itself.
- Check the unitNanometres or micrometres? A sauna blanket with a specification in nanometres around 800 does not fit with far infrared, and that difference is big.
- See whether the range fits the deviceA panel should be in the range of red and near infrared, a blanket in the far infrared. If everything is mixed up, be alert.
- Be wary of superlatives with numbersTerms like the most powerful wavelength or the deepest penetrating frequency are sales, not technology. A wavelength is a property, not a level.
- Ask about what isn't statedWhich seven values exactly, what power, measured at what distance. A shop that can't or won't say often doesn't know itself.
What to look out for
The pitfalls around this topic are always the same. These are the ones you see most often.
- Confusing nanometres with micrometres. 850 nm and 8.5 µm differ by a factor of ten and belong to completely different devices.
- Thinking red light is heat. A panel that stays cool is not weak. Warmth belongs to far infrared, not to red light.
- Thinking infrared is the same as UV. UV is on the other side of the visible spectrum, below 380 nm. Infrared is not UV and does not tan.
- Seeing a higher number as better. 940 nm is not more powerful than 660 nm, just different.
- Believing penetration depths in millimetres. Such figures are rarely backed up and differ per tissue and measuring method. They almost always appear in an advert and rarely in a source.
- Finding wavelength more important than distance and time. Those are the two things you control yourself.
- Automatically thinking more wavelengths is better. Look at size, build and ease of use first.
- Expecting a spectrum to guarantee an outcome. A number on a box says nothing about what you will experience.
And one honest point: if you are mainly looking for warmth and relaxation, you don't need to worry about nanometres. Then a sauna blanket or a lamp is the logical choice and the whole wavelength story is no more than background for you. It only becomes relevant once you look specifically at red light and near infrared.
- Works with far infrared, the warmth you feel on your skin
- Durable PU leather finish, made for daily use
- A roomy model for a warm moment of rest at home
- 60 days to change your mind and a 2 year warranty
In closing
Wavelengths are not a ranking but a map. Red light and near infrared, roughly 600 to 1000 nm, are light that goes into the skin and gives off hardly any warmth. Far infrared, from 3 µm upwards, is radiant heat you feel straight away. A red light panel sits in the first range, a sauna blanket in the second, and neither is better than the other: they do something different.
Once you know which range a device works in, you can read any product page in thirty seconds. If you want to look further into warmth, take a look at the infrared sauna blanket collection. If you are looking for the evidence behind red light and near infrared, it is collected in the Luxyor knowledge base.
Frequently asked questions
What is near infrared?
Near infrared is radiation with a wavelength of about 780 to 1400 nanometres. It lies right next to visible red light and is invisible, but otherwise still behaves like light and not like heat. Red light panels usually work with values around 810, 850 or 940 nm.
What is far infrared or FIR?
Far infrared is the part of the spectrum from about 3 micrometres, so 3000 nanometres and above. This radiation is almost completely absorbed in the upper layers of the skin and becomes heat there. An infrared sauna blanket and an infrared cabin work in this range.
What is a nanometre?
A nanometre, abbreviated nm, is a billionth of a metre. It is the usual unit for the wavelength of light. Visible light runs from about 380 to 780 nm. Far infrared is measured in micrometres, and a micrometre is a thousand nanometres.
Why are 660 nm and 850 nm on almost every panel?
These two values are used most often in research on red light and near infrared, so most is known about exactly these wavelengths. Manufacturers therefore choose LEDs that are close to those values. 660 nm is deep red and visible, 850 nm is near infrared and you can barely see it.
Is a longer wavelength better?
No. A wavelength tells you what kind of radiation you get, not how much or how good. 940 nm is not stronger than 660 nm, just different. Beyond a certain point, radiation is absorbed more and more at the surface and becomes heat instead of light that travels further.
Which wavelength does an infrared sauna blanket use?
A sauna blanket works with far infrared, expressed in micrometres rather than nanometres. Every warm surface emits infrared, and at the temperature of a heating element its peak lies somewhere around eight to ten micrometres. That is physics, not a setting.
What does seven wavelengths mean on a red light panel?
It means there are LEDs with seven different values in the same panel. On the Luxyor Lumi panels that range runs from 480 to 940 nanometres, with the emphasis on 660 and 850 nm. The total power is divided across those LEDs, so more wavelengths does not mean more of everything.
Is red light the same as infrared?
No, but they lie next to each other. Red light is the last part of visible light, about 620 to 780 nm. Above that, infrared begins and seeing stops. The difference in experience is big: red light you see and hardly feel, far infrared you do not see and feel straight away.
Is infrared the same as UV radiation?
No. Ultraviolet is at the short end of the visible spectrum, below about 380 nanometres. Infrared is at the long end, above 780 nanometres. They are opposite ends, and infrared does not tan or burn the skin the way UV can.
How deep does near infrared reach into the skin?
Longer wavelengths in the range from red to near infrared are absorbed less by water and blood than blue or green light, so they travel further into tissue. Concrete depths in millimetres are hard to pin down, because they differ per tissue, person and measuring method. The background is in the Luxyor knowledge base.
Can you see near infrared light shining?
Barely. At around 850 nm you see at most a faint dull glow if you look straight into it, and at around 940 nm usually nothing. That does not mean those LEDs are broken. Do not look straight into a panel for long, and use suitable glasses with bright devices.
What should I look out for with claims about wavelengths?
Check whether concrete values in nanometres or micrometres are given, whether the unit matches the type of device, and whether someone can tell you exactly which values are included. Superlatives such as most powerful wavelength or deepest penetrating are sales talk. Power, distance and size say more in practice.
