How Do You Properly Measure Intensity of Red Light Therapy? - Affordable and Accurate Power Meters
Most people are realizing that the intensity numbers are being false-advertised in MOST red light panel brands. The root cause has been that ignorant manufacturers used cheap solar power meters to measure intensity, which we have proven time and time again to read falsely high by over 2x.
This means that most panels which claim >100 mW/cm^2 at 6 inches or whatever, are actually delivering less than HALF of that amount. That's a big problem!
Of course we know that intensity, often reported in clinical studies in units of mW/cm^2 (milliWatts per centimeter squared), is an important piece to understanding the dosage and efficacy of Photobiomodulation products.
While the science doesn't tell us exact dosing protocols for various conditions, we know we don't want too much intensity, or too little intensity.
To help combat the misinformation in this industry, we are listing out the TOP choices for getting accurate intensity measurements which we have been compiling over the years. Including professional 3rd party labs!
And we will prove in this blog that proper measurements are very affordable!
Laser Power Meters:
Lets say you are a light therapy enthusiast that wants to take your own proper measurements. Or you bought a red light therapy product and want to verify it meets outputs the intensity that it claimed. Then you probably are searching for an adequate power meter to measure your red light panel!
There are some professional grade power meters from:
Even a low-cost system from one of these brands only costs about $1500, which isn't too bad.
However, here are some affordable laser power meters that we have found and tested so far:
- SANWA Laser Power meter (~$273) - our top pick still - the next two do have more error especially at higher intensities.
- UT385 Laser Power meter from UNI-T (~$189) - sold on eBay, AliExpress, and Alibaba
- LaserBee HLPM II and Multi-meter (~$100)
Update! Affordable Solar Power Meter Correction Factors
Even cheaper than a laser power meter is to use a Solar Power Meter and apply a correction factor that we have developed by having Solar Power Meters correlated to 3rd party measurements.
Part 1: Tenmars TM-206
Part 3: TBD
In fact this technique is likely MORE accurate than a laser power meter, since we do a perfect curve fit calculator to adjust the measurements to match the 3rd party lab data.
How to Use a Laser Power Meter:
- The output is in mW, so you need to divide the measurement by the sensor area (basic geometry) to get mW/cm^2.
- They have a wavelength sensitivity curve, so you need to multiply by a proper correction factor (usually provided) or type in the wavelength setting.
Here is an example:
Intensity measurements of our GembaRed Spazer at 6 inches away.
So we have our measurements for each laser power meter on our GembaRed Spazer. We need to choose an "average" correction factor for these meters because the Spazer has 3 wavelengths, then we divide by the area of the sensor.
- SANWA - 11 mW * 0.80 / 0.636 cm^2 = 13.8 mW/cm^2
- UT385 - 8.32 mW / 0.636 cm^2 = 13.1 mW/cm^2
- LaserBee - 1.2 mW * 0.90 / 0.09 cm^2 = 12 mW/cm^2
Compared to our report from Lightlab International of 13 mW/cm^2, these measurements are quite impressive!
So we can see there is a bit of "technique" for interpreting the results and estimating the correction factor for multiple-wavelength units. But ultimately we get a VERY accurate result compared to our professional lab's report, within 8% accuracy!
And no surprise here, the Solar Power Meter measured 25 mW/cm^2, nearly DOUBLE what the laser power meters and professional lab measures.
While I am sure I would make more money claiming 25 mW/cm^2 versus 13mW/cm^2, I know that is a fake number and would be false advertising.
3rd Party Professional Testing:
If you are a professional, manufacturer, brand, reseller, or even dropshipper - then you probably need the most accurate, unbiased measurements possible to avoid liability for improper measurements.
Even if you invest a ton of money into a fancy measurement system, these labs also:
- Have trained professionals to properly take the measurements and interpret the results.
- Keep the equipment calibrated.
- Use industry-standard test methods for repeatability.
- Take measurements in a proper environment controlling stray light.
GembaRed reached out to a 3rd Party Lab before selling a single panel, because we know we aren't experts in optical measurements. So we let them do their jobs and are the only panel company that had transparent 3rd party measurements advertised from day 1. While this should be a normal thing for brands to have accurate measurements, it is quite the opposite with this current industry.
Over our years of research in this industry, here is our list of 3rd Party Labs that can measure red light panels and potentially other photobiomodulation devices:
- LightLab International (lab that GembaRed uses)
- ITL Boulder (lab that Joovv, MitoRed, and others use) *Update 1/13/2021: they no longer do photo-metric testing and most brands have switched to LightLab International*
- Laser Compliance
Now brands will cry that they can't afford 3rd party measurements. But my last invoice from LightLab International was about $250 for just intensity measurements of a panel! But I might be getting a frequent-customer discount at this point - I get a lot of testing done.
A screenshot of part of our test report from Lightlab International for our GembaRed Reboot body-light.
3rd Party labs often have the capabilities to measure much more than intensity! If you care about the science and proper advertising, you can also ask for quotes for even more parameters of your red light panel!
- Spectrum (Wavelengths, nm)
- Total Optical Output (Watts)
- Flicker (Frequency, Percent, and Index)
- Beam Angle
- Isoirradiance Plots
ALL of these factors will be important as this industry gets more sophisticated. However, right now we need to focus on getting accurate intensity for the industry.
Now we have some accurate and affordable options for measuring intensity! When consumers are informed of the truth, they can demand for better numbers from manufacturers.
The UT385 laser power meter has a neat feature that you can enter-in the wavelength you are measuring and not need to do the math of the correction factor. It is already programmed in. So all we need to do is divide by the sensor area of 0.636 to get intensity. Here we see the GembaRed Beam at a few inches away, the laser power meter says 13.54mW / 0.636cm^2 = 21.3 mW/cm^2. Which our 3rd party measured 20mW/cm^2 at 3 inches away. Not bad for a quick test.
We also can't trust delusional scammers using PAR meters. Which PAR stands for Photo-synthetically Active Radiation - basically another grow light meter like how Solar Power Meters are used. You still need to convert the units to mW/cm^2 (so its not actually a flat spectral output for intensity) and after all the effort, you are better off with a more affordable solar power meter anyway which gives more meaningful measurements.
How many photobiomodulation studies use Solar Power Meters or PAR meters? ZERO. No self-respecting scientist or "expert" would use one of them. It is a quick litmus test to tell who the fake "experts" are out there.
Many brands will give you a laundry-list of clever excuses why they use Solar Power Meters. They have read my blogs and keep coming up with new ways to lie to you.
What started out as ignorance, is now a scam and cover-up.
The real reason companies can't be honest is that they will lose money, plain and simple. They care more about claiming some fake high intensity number to make easy money than about science, ethics, or the law.
So, if you even suspect any lies from a brand that claims >100mW/cm^2 at 6 inches (or higher!), send them this article and ask for a measurement from one of these test methods.