Ask ten red light brands for the irradiance of their panels and you will get ten confident numbers, most of them meaningless. This page explains what we measure, how we measure it, what our RLF panels actually produce, and why we publish a range rather than one flattering headline figure.
Who builds these panels
The directors of Dermfix have been manufacturing medical phototherapy devices using narrowband UVB since 2009. That work is done under ISO 13485 with CE and MDSAP approval, and those devices have been assessed by TÜV SÜD in Germany, the MHRA in the UK, the TGA in Australia and Health Canada. Class IIa phototherapy is a slow, documented, audited business, and it is where our habits around measurement come from.
Our 2025 RLF range of red light panels is designed and built for Dermfix Ltd to the same internal standards. Red and near-infrared wavelengths do not require Class IIa medical device certification in the way UVB does, which keeps approval and production costs down — and keeps the retail price down with them. That is a genuine difference in regulatory burden, not a shortcut in build quality.
The standard that actually applies
A red light panel that emits above 780nm is, in regulatory terms, an appliance incorporating infrared emitters intended for skin exposure. In Great Britain that puts it under the Electrical Equipment (Safety) Regulations 2016, and conformity is normally demonstrated against BS EN 60335-2-27 — “Particular requirements for appliances for skin exposure to optical radiation”. It is the same technical content as the EN 60335-2-27:2014 standard used across Europe.
We hold EN 60335-2-27 test documentation for the RLF range. A great many panels sold into the UK do not, and there is no easy way to tell from a product page. So ask. One email — “can you send me your EN 60335-2-27 test report?” — separates the brands that have done the work from the ones that have bought a container and written a listing.
Worth knowing if you are comparing sellers: under UK product safety law, a business that puts electrical equipment on the market under its own name or trade mark is treated as the manufacturer. It carries the testing and compliance responsibility itself. It cannot point at a factory in Shenzhen. Plenty of white-label brands appear not to realise this.
How we measure irradiance
For day-to-day in-house testing we use a Hopoocolor OHSP350IR spectrometer. For anything that matters we use approved third-party laboratories with calibrated medical-grade spectrometers. Those laboratory reports live in our technical file and are not published, for the same commercial reasons every manufacturer keeps its technical file closed.
What we do not use is a solar meter. The Solarmeter Model 9.6, the Tenmars TM-206 and the TES-1333 all turn up in competitor marketing as evidence for output figures. They are broadband instruments designed for sunlight. Point one at a narrow-band LED array and it will happily produce a large number that has very little to do with the therapeutic dose reaching your skin. A spectrometer measures irradiance per wavelength; a solar meter measures something else and reports it in the same units.
Why one number can never describe a panel
Light from an LED array spreads, scatters and overlaps. The highest reading on any panel is dead centre, on axis, at close range. Move towards the edges, or up and down the panel, and the figure falls. That is not a defect and it is not specific to our panels — it is how light behaves, and it is true of every panel on the market including the ones quoting a single number.
Which is why a headline irradiance figure tells you almost nothing on its own. Three things have to travel with it: what was measured, at what distance, and on what instrument. A figure without all three is decoration.
What our panels produce
Measured at 15cm on full power, our panels typically peak at around 100 mW/cm² at the very centre. For working out treatment times, we would rather you used a realistic average across the treatment area: around 80 mW/cm² on the larger panels, and around 60 mW/cm² on the smaller ones.
Publishing the average rather than the peak makes our specification look weaker next to brands quoting centre-point maximums. We think it is the more useful number. Once you have spent time with a spectrometer and watched readings move across a panel face, quoting a single peak starts to feel like a sales decision rather than a technical one.
What to do with these numbers
Irradiance is only half of a dose. The other half is time: energy delivered (in joules per square centimetre) is irradiance multiplied by exposure duration. A lower-irradiance panel used for longer delivers the same joules as a higher-irradiance panel used briefly.
That matters because more is not automatically better. Photobiomodulation is widely described as having a biphasic dose response — Huang and colleagues set this out in Dose-Response in 2009 — where too little energy does nothing and too much can be less effective than the optimum. Chasing the highest possible irradiance figure is not obviously the winning strategy it appears to be. A moderate, consistent, slightly longer session is a sensible way to reach a target dose.
And 80 mW/cm² as a working average is a strong output by any measure. These are bright, powerful panels. If a competitor claims 150+ mW/cm² with no distance stated, no instrument named and no report available, treat the number as marketing until proven otherwise.
Five questions worth asking any UK seller
- What is the irradiance, at what distance, measured on what instrument?
- Is that a centre-point peak or an average across the panel?
- Can I see your EN 60335-2-27 test report?
- Who is the legal manufacturer — you, or someone else?
- Where does a warranty claim physically go, and who pays the carriage?
Any brand that has done its homework can answer all five without hesitating. We have written more on this in our UK buyer's guide to red light therapy panels.