What Almost Everyone Doesn't Understand About Red Light Therapy Masks

By Scott Chaverri, founder and CEO of Mito Red Light | Updated October 12, 2026

The short answer: When you compare LED face masks, what matters isn't how bright the individual LEDs are. It's how much light reaches your entire face, and how evenly that light is spread. Most mask reviews and spec sheets measure the light directly over one LED, and that hides two problems:

1. The face-wide average is far lower than the number you see. On common skin-contact silicone masks, the LEDs cover only about 2% of the face. Counted across the whole face, these masks deliver roughly a tenth of what MitoGLOW does.
2. The light is uneven. Bright spots over each LED, very little light in between. A 2026 peer-reviewed study measured up to a 40-fold difference in light from one part of the face to another on a skin-contact mask.

I've followed Dr. Josh Axe's work for years, and I respect what he's done to educate people about health. His article "The Best Red Light Therapy Masks of 2026" gets one big thing right: masks should be scored on measured light, not marketing claims.

But the measurements behind that ranking, like pretty much all mask reviews, miss both problems, (and measured output is 25% of every mask's score). I whipped up this article to explain.....

 

Key takeaways

• A reading over one LED isn't a whole-face dose. It measures the brightest spot on the mask.
• New 2026 research: a peer-reviewed study in Photochemical & Photobiological Sciences found light varied about 40-fold and 21-fold across the face on two skin-contact masks, and concluded that "different regions of the face may receive substantially different doses during the same session."
• An independent lab measured the gap: 63.7 mW/cm² over the LEDs of a silicone mask, but about 1.46 mW/cm² averaged across its whole surface.
• More light isn't always better. Red light therapy works at modest doses, so what matters is getting a consistent dose to the whole face.
• MitoGLOW's hover design holds its 266 LED packages off the face so their light overlaps: zero gaps.

 

The hidden problem with LED mask ratings

Imagine judging how well a room is lit by holding a light meter directly under one spotlight. You'd get an impressive number, and it would tell you almost nothing about the rest of the room. That's how most LED masks are measured (and marketed).

There are two very different numbers you can report for a mask:

• Peak irradiance: the reading with the sensor directly over an LED. It tells you how bright one LED is.
• Face-wide average irradiance: the light averaged across the entire treated area, including the spaces between LEDs. It tells you what your face actually receives.

(Irradiance is light intensity, measured in milliwatts per square centimeter, or mW/cm². Dose is intensity multiplied by time, measured in joules per square centimeter, or J/cm².)

Allow me for a moment to "exaggerate to make a point" - imagine: a skin-contact mask with a single LED over one cheek, measuring 100 mW/cm² directly on the LED. A ranking built on on-LED readings would put it first, because 100 mW/cm² beats every mask on the list. Averaged across a face of about 300 cm², that single 0.1 cm² LED delivers about 0.03 mW/cm², almost no light at all. Peak irradiance describes the LED. The face-wide average, and how evenly it's delivered, describes the treatment.

 

Why the distance between LEDs and skin matters

Each LED sends out a cone of light that widens with distance. When the LEDs sit right against the skin, the cone has no room to widen, so each LED lights a small spot and the skin between LEDs gets very little light. When the LEDs are held off the face, each cone widens and overlaps its neighbors' before it reaches the skin, so the light arrives evenly. Optics research on LED arrays confirms that even light requires LED spacing matched to the distance from the surface (Moreno et al., Applied Optics, 2006), and a 2025 review of LED therapy devices notes that in wearable devices, "insufficient illumination persists in the gaps between LEDs" (Wang et al., Light: Science & Applications, 2025).

 

What new 2026 research found

In May 2026, researchers from Universidad San Pablo CEU in Madrid and the University of Barcelona published the most detailed independent measurement of consumer LED face masks we've seen: "Spectral emission variability in commercial LED masks for cosmetic use" (Baeza-Moyano, Bernardez & Sola, Photochemical & Photobiological Sciences, 2026). The authors bought the masks with university research funds and declared no competing interests.

How they measured

• Four commercial masks, chosen for wide online availability, prices of about €13–200, common LED colors and different designs, including different distances between the LEDs and the face.
• A laboratory-grade instrument: a double-monochromator spectroradiometer, calibrated at the Institute of Optics of the Spanish National Research Council (CSIC) against Spain's national standard.
• A fixed sensor, so readings weren't affected by hand placement.
• Two kinds of design: two masks are worn in direct contact with the skin; the other two hold the face about 2.5 cm and 8 cm from the LEDs.

What they found on the skin-contact masks

Light varied enormously across the face. The researchers took readings at several facial regions on both contact masks:

Skin-contact mask	Lowest reading	Highest reading	Spread
Mask #2	0.11 mW/cm²	4.38 mW/cm²	about 40-fold
Mask #4	0.14 mW/cm²	2.94 mW/cm²	about 21-fold

In the authors' words, the results were "highlighting large spatial differences in the energy received," and "different regions of the face may receive substantially different doses during the same session."

LED spacing was irregular. Gaps between LEDs ranged "from about 0.5 cm to 1.5-3.0 cm, depending on the region," with irregular spacing in areas such as the forehead and chin.

Fit makes it worse. Contact masks are meant to sit on the skin, but "depending on the user's facial anatomy, they might not fit uniformly."

The real spread is likely even larger. The sensor's diffuser was 1.5 cm wide, so each reading already averaged light over an area much bigger than an LED. A pinpoint sensor at the skin would show brighter peaks and darker gaps.

What they found on the masks held away from the face

The researchers didn't need to map the two masks that hold the face 2.5–8.5 cm from the LEDs, "due to the greater distance between LEDs and face (2.5–8.5 cm), which means that radiation reaches it from more angles." In those masks, "the distribution of LEDs is more regular." That's the same principle as the side-view illustration above.

Why the authors say it matters

• Dose is everything: "therapeutic outcomes depend critically on the radiometric dose: insufficient irradiance or exposure time may result in subtherapeutic stimulation, whereas excessive radiant exposure may trigger adverse or counterproductive responses."
• Mask specs can't be taken at face value: "None of the devices include spectral irradiance data," and one manual listed a "light blue" wavelength of 160–195 nm, which is ultraviolet-C, not visible light.
• Masks that look alike aren't alike: with similar session times, users were exposed to irradiances "that differ by more than an order of magnitude," and "devices labeled with the same nominal color cannot be assumed to produce equivalent effects."
• Measure the light properly: the findings "underscore the importance of characterizing both the spectral and radiometric properties of facial LED masks to ensure consistent and effective photobiomodulation outcomes."

The study measured these spatial differences with the masks' blue LEDs. The geometry that creates them, LEDs against the skin and centimeters apart, applies to every color on a contact mask. The study didn't test MitoGLOW, KALA or HigherDOSE; what it shows is why measuring the whole face, and how evenly it's lit, matters.

 

Problem 1: The face-wide average is far lower

What's measured, and what's calculated

The evidence comes in three layers, and it's worth keeping them separate:

1. Measured (2026 study): light varied 40-fold and 21-fold across the face on two skin-contact masks.
2. Measured (independent lab): on a 155-LED silicone mask, Light Lab International found 63.7 mW/cm² directly over the diodes, peaks covering "only about 2.2% of the mask's total surface area," and about 1.46 mW/cm² averaged across the whole surface (Light Therapy Insiders). That's a 44-fold gap on the same mask.
3. Calculated, and confirmed by that lab data: multiplying the peak reading by the share of the face the LEDs cover. For the lab-tested mask, 63.7 × 2.2% ≈ 1.4 mW/cm², matching the measured 1.46.

The LEDs cover about 2% of your face

We measured a typical 66-LED flexible silicone mask, the layout used by several popular brands:

	Value
LED package size	about 1/8 × 1/8 inch (3.2 × 3.2 mm), about 0.10 cm²
Total LED area (66 packages)	about 6.7 cm²
Treated area inside the mask	about 265–340 cm²
Share of the face directly under an LED	about 2–2.5%

 

Admittedly, light does spread a little beyond each LED and scatters within the skin, but only over a few millimeters, while the LEDs on these masks are 20–25 mm apart. A 66-LED mask also has fewer than half the LEDs of the lab-tested 155-LED mask, so its gaps are larger still.

What the ranking looks like with face-wide averages

Mask	Figure Dr. Axe scored	Face-wide average (coverage calculation)
KALA (66 LEDs, skin contact)	26 mW/cm²	about 0.5–0.65 mW/cm²
HigherDOSE (66 LEDs, skin contact)	26 mW/cm²	about 0.5–0.65 mW/cm²
MitoGLOW (266 LED packages, hover design)	5.7 mW/cm²	5.7 mW/cm²

 

Dr. Axe's own article says KALA's reading was taken "directly over the red and near-infrared LEDs, so the average across your face is likely lower" (Dr. Axe), yet that reading counts at full value in the score. HigherDOSE, on the same 66-LED layout, measured exactly the same 15.6 J/cm² in 10 minutes (Light Therapy Insiders). Counted across the whole face, these contact masks deliver roughly a tenth of what MitoGLOW does.

The 26 mW/cm² reading itself is also hard to rely on, because readings taken in contact with an LED are very sensitive to technique. We explain why in Appendix A.

Problem 2: The light is uneven

A low average is only half the problem. The light that does arrive is concentrated in bright spots over each LED, with very little light in between.

What this means for your skin

You buy an LED mask hoping to improve your skin's appearance across your whole face. If some areas get many times more light than others, they get very different doses. Red light therapy has a dose window: too little light does little, and more light isn't always better. Light therapy researchers describe this as a biphasic dose response, where too much can reduce the benefit (Huang et al., Dose-Response, 2011). In human skin cells, 5 J/cm² of red light stimulated healing activity, while 10 and 16 J/cm² reduced cell viability (Hawkins & Abrahamse, Lasers in Surgery and Medicine, 2006). Uneven light leaves much of the face far below the intended dose. Even light across the whole face is what the science calls for.

Other fields that use light as medicine already require even light, from infant jaundice lamps to photodynamic therapy. We cover those standards, and the research on even versus uneven beams, in Appendix B.

 

Why even light matters: what the research shows

The same dose at different intensities gives different results. In a wound-healing study using 670 nm LEDs, the same 5 J/cm² produced different outcomes depending on how irradiance and time were combined: "Varying irradiance and exposure time to achieve a specified energy density affects phototherapy outcomes" (Lanzafame et al., Lasers in Surgery and Medicine, 2007). Hot spots plus dark gaps are not equivalent to the same average delivered evenly.

Even beams produce even biological responses. When researchers compared a uniform "flat-top" beam with a standard beam that's brighter in the center, "ATP synthesis was increased homogenously in the flat-top handpiece, both in the centre and the edges of the beam," while cells at the edges of the uneven beam responded less (Amaroli et al., International Journal of Molecular Sciences, 2021). A similar comparison found the uniform beam improved bone-cell maturation (Hanna et al., Frontiers in Endocrinology, 2019).

Small spots penetrate less. In skin modeling, penetration rises noticeably as the beam widens from 1 to 5 mm (Ash et al., Lasers in Medical Science, 2017).

 

We're not the only ones critical of skin-contact masks

In June 2024, Carter Gottlieb, an MD/PhD candidate who posts evidence-based skincare content as @evibacarter, put a spectroradiometer on popular LED masks and showed the same pattern on camera: bright spots directly over each LED, and readings falling toward zero in the gaps between them (Eviba Carter on TikTok).

We agree with Carter that silicone skin-contact masks have real design problems: most of the face sits between LEDs, the light arrives in hot spots, and the fit changes from face to face.

But we disagree with Carter that it is impossible to make a good mask. We spent a year developing the MitoGLOW (patent-pending for both design and utility) in an attempt solve for these exact issues!

We also disagree with his conclusion that a mask needs panel-level irradiance to help skin. High fluences aren't needed, and the clinical evidence shows it. In a 2025 randomized, double-blind, sham-controlled trial, a home LED mask with a maximum of 10 mW/cm² of red and 10 mW/cm² of near-infrared light, used for 9 minutes five times a week, improved crow's feet by at least one grade in 86% of users as scored by independent raters, compared with 17% of users of a sham mask (Park et al., Medicine, 2025). Manufacturer-run studies of flexible silicone masks have also reported improvements in wrinkles, texture and elasticity (Omnilux).

So silicone contact masks can help skin, in spite of their design. The point isn't that they do nothing. A mask that delivers its light evenly across the whole face is what the science calls for: light therapy doses are defined per square centimeter of skin, and every field that uses light as medicine requires even light. That's what MitoGLOW was built to do.

 

Why MitoGLOW was built differently

We designed the MitoGLOW LED mask more than two years ago, and spent over a year developing it, to solve both problems. Instead of pressing LEDs against the skin, its rigid hover shell holds them off the face, so each LED's light widens and overlaps its neighbors' before it reaches the skin: the light reaches the face "from more angles," as the 2026 study put it. With 266 LED packages (1,064 individual chips), four times as many as a 66-LED contact mask, there are zero gaps: even light across the face instead of peaks and valleys.

That's also why we state a conservative whole-face dose of 3 J/cm² per 10-minute session instead of a peak figure. When Light Therapy Insiders tested MitoGLOW, it measured 3.4 J/cm², more than we claim (Light Therapy Insiders). As far as we can tell, it was the only mask in Dr. Axe's ranking that delivered more than its maker states.

Publishing honest, independently measured numbers isn't new for us. Since 2019, we've had our red light therapy panels tested by LightLab International, an ISO/IEC 17025-accredited photometric lab, and published the results: average irradiance across the treatment area, minimum and maximum readings, uniformity, iso-irradiance maps and full spectra, not just a peak figure. You can see every report on our independent lab test data page. That page covers our panels; the MitoGLOW figures in this article come from Light Therapy Insiders' testing.

MitoGLOW also includes four wavelengths (465, 590, 630 and 830 nm) and five modes, built-in chin and neck coverage, full blackout eye protection, and a rigid, hygienic shell that's easy to clean. MitoGLOW is FDA-cleared for the treatment of full-face wrinkles.

 

How to compare red light therapy masks fairly

Before you buy, ask two questions of any mask spec or review: what's the face-wide average, and how even is the light? Then check how it was measured. Three methods work, as long as every mask is measured the same way:

1. Peak × coverage: for skin-contact masks, multiply the on-LED reading by the share of the face the LEDs cover. It's a quick, realistic estimate of the average.
2. A full grid: take readings at evenly spaced points across the whole treated area, including the gaps between LEDs. The grid also shows evenness: the lowest reading as a share of the average.
3. Total output ÷ treated area: measure the mask's total light output in an integrating sphere and divide by the area it treats. It doesn't depend on where a sensor is placed.

A trustworthy review should also say where the sensor was placed, how far it was from the LEDs, the sensor's size and calibration, and the mode tested, as light therapy reporting guidelines recommend (Jenkins & Carroll, Photomedicine and Laser Surgery, 2011; Hadis et al., Lasers in Medical Science, 2016). Be wary of any mask that quotes a single big mW/cm² number without saying where it was measured. This is where Dr. Axe's ranking falls short: it compares on-LED readings from contact masks with a whole-face figure from a hover mask, which aren't the same kind of measurement.

For more on choosing a mask, see what to look for in a red light therapy mask, how LED face masks work and what the research supports, and red light therapy mask vs panel.

 

Frequently asked questions

What did the 2026 LED mask study find?

Researchers from Universidad San Pablo CEU and the University of Barcelona measured four commercial LED face masks with a calibrated laboratory spectroradiometer (Photochemical & Photobiological Sciences, May 2026). On the two skin-contact masks, light varied about 40-fold and 21-fold across different parts of the face, and the authors concluded that "different regions of the face may receive substantially different doses during the same session." They also found that none of the masks came with spectral irradiance data, and that irradiance differed by more than tenfold between masks with similar session times.

What is a good irradiance for a red light therapy mask?

Look at the face-wide average and how evenly it's delivered, not the peak. A mask with a modest but even face-wide average delivers more useful light than a mask with a high peak reading and dark gaps between LEDs. Dose matters too: MitoGLOW delivers a conservative 3 J/cm² across the face in a 10-minute session.

Do LED face masks have dead spots?

Skin-contact masks do. When LEDs sit right against the skin, each one lights only a small spot, and the skin between LEDs receives very little light. On a typical 66-LED silicone mask, the LEDs cover about 2–2.5% of the face, and a 2026 study measured up to 40-fold differences in light across the face of a skin-contact mask. Hover designs like MitoGLOW hold the LEDs off the face so their light overlaps.

Do silicone LED face masks work?

They can help. Red light therapy doesn't require very high irradiance: in a 2025 randomized, sham-controlled trial, a home LED mask with a maximum of 10 mW/cm² of red and near-infrared light improved crow's feet in 86% of users, compared with 17% with a sham. But skin-contact silicone masks deliver their light unevenly, with bright spots over each LED and little light between them, so much of the face gets far less than the intended dose. Delivering light evenly across the whole face, as MitoGLOW's hover design does, is what the science calls for.

Why is uneven light a problem in red light therapy?

Light therapy works within a dose window: too little light does little, and more light isn't always better. Uneven light puts small patches of skin at high intensity and leaves much of the face far below the intended dose. Research comparing uniform and uneven beams found more consistent biological responses with uniform light.

Why do some mask reviews report very high mW/cm² numbers?

Usually because the reading was taken with the sensor directly over an LED. That measures the brightest spot on the mask. One lab measured 63.7 mW/cm² over the LEDs of a silicone mask but about 1.46 mW/cm² across its whole surface.

Why are readings taken directly on a mask's LEDs unreliable?

Within a few millimeters of a small LED, the reading changes sharply with tiny shifts in the meter's height, alignment, angle and sensor size, and pressing a meter into a soft silicone mask changes the geometry. A single on-LED number with no distance or position recorded can't be reproduced, and it measures the brightest spot rather than what the face receives. When calibrated laboratory instruments measure silicone contact masks, they find around 1 mW/cm² or less.

How should red light therapy masks be measured?

The same way for every mask, with the face-wide average as the headline number and evenness reported alongside it: an evenly spaced grid across the treated area (including the gaps between LEDs), total output divided by treated area, or, for contact masks, the on-LED reading multiplied by LED coverage.

Is MitoGLOW FDA-cleared?

Yes. MitoGLOW is FDA-cleared for the treatment of full-face wrinkles.

 

We've shared this with Dr. Axe

On October 10, 2026, we emailed Dr. Axe and his team to explain these measurement problems, with our calculations in a short summary: Why a Reading Over One LED Isn't a Whole-Face Dose (PDF). We'll update this article if and when we hear back from Dr. Axe and his team. We've also offered to send MitoGLOW to Dr. Axe and to Light Therapy Insiders for testing under any fair, published method.

 

The bottom line

When you compare LED face masks, what matters isn't how bright the individual LEDs are. It's how much light reaches your whole face, and how evenly. A reading over one LED on a skin-contact mask measures about 2% of your face and hides both problems: a far lower face-wide average, and light delivered unevenly. A 2026 peer-reviewed study has now measured that unevenness on commercial masks. Count the whole face, measure how evenly it's lit, and the ranking changes.

See how MitoGLOW's hover design works, read more about red light therapy for the face and neck, and learn how often to use a red light therapy mask. For more of the science behind red light therapy, explore our Research Evidence Hub.

 

Appendix A: Why readings taken on a contact mask are so error-prone

This appendix adds to the main argument but isn't required for it. Even if every on-LED reading were perfectly accurate, the two problems above would still stand.

Dr. Axe's output scores come from Light Therapy Insiders' measurements, and the 26 mW/cm² credited to KALA and HigherDOSE is the number most worth examining. Light Therapy Insiders uses a handheld spectrometer, a good tool for this work (we use the same model ourselves). The problem isn't the meter. It's that measuring light from an LED pressed against the skin is one of the hardest measurements in light therapy, and small differences in technique produce very different numbers.

What the reviews disclose

For KALA, the review says only: "I measured 26 mW/cm² directly over the red and near-infrared LEDs" (Light Therapy Insiders). It doesn't say how far the sensor was from the LED, whether it touched the mask, how many readings were taken, or which reading was reported. For HigherDOSE, the review says "I moved the spectrometer across the mask surface" and gives a dose of 15.6 J/cm², with no positions, distances or individual readings, while describing "surprisingly consistent power readings" (Light Therapy Insiders). That's hard to reconcile with LEDs covering about 2% of the mask unless the readings were taken over LEDs.

Light Therapy Insiders acknowledges the limitation itself. In September 2026, it wrote that a spectrometer "measures the light reaching its sensor at one particular point, distance, and moment... It does not automatically tell me what is happening across the panel's entire treatment area" (Light Therapy Insiders). It added an integrating sphere so that "upcoming reviews, particularly those involving masks," would include more comprehensive testing. The KALA (July 2025) and HigherDOSE (November 2025) figures were measured before that.

Seven ways a contact reading goes wrong

1. Height. Within a few millimeters of an LED, light intensity changes steeply with distance. In a simple optics model of a bare LED, lifting a small sensor just 1 mm, from 1.5 mm to 2.5 mm above the LED, cuts the reading by about 64%. On a soft silicone mask, that's the difference between resting the meter on the mask and pressing it in.

2. Alignment. In the same model, sliding a small sensor 1 mm sideways off the center of the LED cuts the reading by about half, and 2 mm sideways cuts it by almost 90%. Mask LEDs are only about 3 mm wide, so "directly over the LED" covers a wide range of possible readings.

3. Sensor size. A meter reports light per square centimeter averaged over its own window, not over the skin. In the same model, an LED 1.5 mm away reads about twice as high through a 10 mm window as through a 15 mm one, and a pinpoint sensor would read 12 to 26 times higher than either.

4. Neighboring LEDs. A wide sensor window also picks up light from nearby LEDs. The 2026 study's authors noted that, "owing to the diffuser size and the LED spacing, the irradiance does not correspond solely to the selected LED" (Baeza-Moyano et al., 2026).

5. Steep angles. Up close, much of an LED's light hits the sensor at steep angles. A meter's diffuser is designed to weight light correctly by angle, and that correction is hardest to get right at the extremes.

6. The mask itself. Pressing a sensor into a flexible silicone mask can tilt the LED, change the distance and flatten the mask in ways that don't happen on a face. KALA's own reviewer found that on a real face, "some areas, like the cheeks, sit flush, while other parts, like the jaw and the sides of the face, float above the skin" (Light Therapy Insiders).

7. Mode and timing. Many masks pulse or cycle through colors, and LED output can shift as the LEDs warm up. A single snapshot can land on a peak, a dip or a transition.

We see all of this in our own testing: a reading taken directly against a mask's LEDs swings wildly when the meter moves by a fraction of a millimeter. That's why measurement guidance stresses measuring "at, or through, relevant targets at specific distances and geometry" and recording how it was done (Hadis et al., 2016; Jenkins & Carroll, 2011).

Solar meters make it worse

Many brands' advertised mW/cm² figures come from handheld solar meters. Light Therapy Insiders warns that these meters "are designed to measure sunlight, not LEDs, and they often read two to three times higher than the actual value" (Light Therapy Insiders). Dr. Axe's ranking checks each mask's measured output against those advertised figures, so the claims being checked may themselves be inflated. It's why we publish accredited-lab averages for our panels rather than solar-meter peaks; see our independent test data.

Handheld readings vs laboratory measurements

The Maysama Aura was measured both by Light Therapy Insiders and by an independent laboratory. The handheld readings ranged "from roughly 3 to 7 mW/cm² across different parts" of the mask, averaging about 5.5 mW/cm². Light Lab International's average across the whole illuminated surface was about 1.46 mW/cm² (Light Therapy Insiders). An average of readings taken over or near LEDs is still a peak-type number.

Source	Mask type	Measured
Light Therapy Insiders, handheld spectrometer (scored by Dr. Axe)	KALA and HigherDOSE, 66-LED silicone contact masks	26 mW/cm², "directly over the red and near-infrared LEDs"
Light Lab International	Maysama Aura, 155-LED silicone contact mask	about 1.46 mW/cm² averaged across the surface (63.7 directly over the diodes)
Baeza-Moyano et al. 2026, calibrated laboratory spectroradiometer	Two skin-contact masks, red LEDs, sensor centered on an LED	0.23 and 0.93 mW/cm²
Baeza-Moyano et al. 2026	All four masks, red LEDs	0.017 to 0.93 mW/cm²; red dose per session 0.01 to 0.84 J/cm²

 

The masks differ, and the 2026 study measured visible light only (380–680 nm), so it doesn't include near-infrared. But the pattern is consistent: when laboratories measure silicone contact masks, they find around 1 mW/cm² or less, not 26.

 

Appendix B: More on why even light matters

Other light-based medicine already demands even light:

• Infant phototherapy: the international standard for neonatal jaundice lights (IEC 60601-2-50) defines the effective treatment area as the zone where the ratio of minimum to maximum irradiance is more than 40%. Moving LED lights closer than recommended raised the peak but lowered the median irradiance and the uniformity (Ismail & Horn, South African Journal of Child Health, 2020), the same trade-off a contact mask makes.
• Photodynamic therapy: "a homogeneous and reproducible fluence rate delivery... plays a determinant role in preventing under- or overtreatment" (Mordon et al., Translational Biophotonics, 2020). When one commercial dermatology LED array was mapped, "the dose fell to 38% of that received at the central area at a distance of only 2 cm" (Moseley, Photochemical & Photobiological Sciences, 2005).
• Research light sources: laboratory LED arrays built for light therapy research are tuned to vary as little as 2.3% across the illumination field (Kercher et al., Journal of Biomedical Optics, 2020).

 

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