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How do you read a lens spectral test report?

By Spektrum Glasses Editorial Team · Published 2026-08-04 · Updated 2026-08-04 · Facts re-checked 2026-08-04 How this page is written and checked: our editorial method · how we verify claims

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Short answer

A spectral transmittance report plots how much light a lens passes at each wavelength. Read four things: which laboratory ran it and whether it is accredited to ISO/IEC 17025, the test method, the exact nanometer band behind every percentage, and the visible light transmission. A percentage with no band attached is marketing, not measurement.
  • Any blue-light percentage without a nanometer range is unverifiable. Demand the band.
  • Our clear lens filters 99.99% at 400 nm but 33.1% at 450 nm.
  • Check lab accreditation (ISO/IEC 17025), test method (ANSI Z80.3), sample ID and date.
  • Visible transmittance shows the cost: our clear lens passes 91.6% photopic light.
  • A transmittance curve is a physics result, not evidence of a health outcome.

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What an accredited spectral report actually contains

A spectral transmittance report measures how much light a lens passes at each wavelength, usually in 5 or 10 nm steps from the ultraviolet through the visible range. Everything else on the page is context for that curve. Before reading a single number, check the header for five things:
  • The laboratory and its accreditation. Our clear-lens report was run by COLTS Laboratories, report O-SPG111015, accredited by A2LA to ISO/IEC 17025 under certificate 1612.01. ISO/IEC 17025 is the international standard for testing-laboratory competence: an outside body audited the lab’s methods and calibration.
  • The test method. Ours states spectral transmittance per ANSI Z80.3, the US standard for non-prescription sunglass and fashion eyewear transmittance. A named method means someone else can reproduce the result.
  • A sample identifier tying the report to one specific lens and tint, not to a product family.
  • The date.
  • The full table or curve, not a single headline figure.
If a vendor shows a colored graph with no lab name, no accreditation, no method and no numbers on the axes, that is an illustration, not a test. Discounting the claim entirely is a reasonable response.

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A percentage means nothing without the band it covers

Blue light is not one wavelength. The band usually discussed runs roughly 400-500 nm, and filtration across it is almost never flat. Four measured points from our clear lens, same COLTS report: Every one of those numbers is true. A brand holding this exact report could print “filters 99.99% of blue light” and point at 400 nm, or “filters 33%” and point at 450 nm. The band is what makes the sentence honest. This matters most for clear lenses, because physics constrains them. A lens that removes most of 450-500 nm is taking a large share of blue out of the transmitted light, and it will look yellow, amber or orange. A near-clear lens filters hard at the short end and progressively less as you move up the band. Ours does exactly that. Our ZENOX clear lens averages about 52% across the blue band with 100% UV filtration: same trade-off, different balance. So when any vendor, us included, quotes a big percentage for a clear lens, the first question is: at what wavelength, or averaged over what range.

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Peak, average, and the number a brand chose to print

A single report can support at least three different numbers, and they are not interchangeable.
  • Peak filtration is the best single wavelength. Our clear lens peaks at 99.99% at 400 nm. Most flattering number on the page, least informative.
  • Band average is the mean across a stated range. Averaging the four clear-lens points above gives (99.99 + 95.1 + 63.0 + 33.1) / 4 = 72.8% across 400-450 nm. That is a crude unweighted average of four sample points rather than the integrated figure a lab computes, and it stops at 450 nm, yet it already sits 27 points below the headline.
  • Filtration at a specific range of interest. Our amber evening lens measures 98.3% across 460-480 nm, the range our report labels the melatonin band, and 97.9% averaged across 400-500 nm.
The gap between peak and average is where misleading marketing lives. When the two are close, the lens is working broadly: our orange lens measures 99.96% across 380-500 nm and our red lens 99.83% over that same range. When they are far apart, as with any near-clear lens, the headline is describing a narrow slice. Ask which of the three you are being shown.

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Read the visible light transmission, not just the blue numbers

Every report worth reading states visible (photopic) transmittance: how much of the light your eye actually uses gets through. This is the cost side of the ledger, and it is the number most often omitted. Our clear lens transmits 91.6% photopic. That is near-clear, with brightness and color rendering close to wearing nothing, which is the entire point of a lens for daytime desk use. It is also why its filtration at 450 nm is only 33.1%. You cannot have both. At the other end, our orange and red lenses buy 99%+ across 380-500 nm by removing a large share of visible light and shifting color. Neither is suitable for driving, and we say so. Standards such as ANSI Z80.3 exist partly to categorize how much light a lens transmits, which is why a report quoting a blue-band percentage with no visible transmittance is hiding the trade-off. Check UV separately. Our clear lens filters UVA and UVB at over 99.99% each; the ZENOX clear lens is at 100% UV. UV filtration is cheap and near-universal in modern lenses, so it is not a differentiator. A brand leading with it is changing the subject.

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What a spectral report cannot tell you

A spectral report is a physics measurement of a piece of plastic. It describes what reaches your eye and nothing about what happens afterward. No transmittance curve, however well accredited, supports a claim about a medical condition, and we do not make one. The published evidence on downstream outcomes is limited and contested. The one optical-performance study cited here, Leung, Li and Kee (PLOS ONE, 2017), measured commercially available blue-light-filtering lenses and found they reduced the calculated blue-light hazard by roughly 10-24%. That is a calculated optical quantity derived from transmittance, not a clinical result, and the width of the range shows how much real products differ. Two consequences. A large blue-band percentage and a large real-world effect are different things: the first is easy to verify, the second is not. And when a vendor page moves straight from a lab number to a statement about how you will feel, it is asserting a link the report does not contain. Judge the number and the promise separately.

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Questions to send any vendor, including us

Paste these into an email. A brand with real testing answers all six in one reply, in numbers rather than adjectives.
  1. Can you send the full lab report as a PDF, including the transmittance table or curve?
  2. Which laboratory ran it, is it accredited to ISO/IEC 17025, by which accreditor, under which certificate number?
  3. What test method and standard was used?
  4. For every percentage on your marketing: peak value or band average, and over exactly which nanometer range?
  5. What is the visible (photopic) transmittance of this lens?
  6. Does the report identify the specific lens and tint I am buying, and what is its date?
Our answers are published at https://kb.spektrumglasses.com/lab-results, with report numbers and per-wavelength figures instead of one headline. If another vendor will not do the same, that refusal is itself information. And if we ever publish a percentage without its band, hold us to this page.

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Where these numbers come from

Every measured figure quoted here is transcribed from a third-party laboratory report, published in full with the wavelength band and the report number: lab results. Our rule for what may appear on this page at all is on how we choose what to publish.