Skip to main content

​
Do blue light reading glasses distort colour?

By Spektrum Glasses Editorial Team · Published 2026-08-11 · Updated 2026-09-11 · Facts re-checked 2026-09-11 How this page is written and checked: our editorial method · how we verify claims

​
Short answer

A clear blue-light reading lens filters a narrow slice of blue and UV wavelengths; at 91.6% visible light transmission ours passes ANSI Z80.3’s transmittance and chromaticity test, so colour stays close to true. Deeper tints - yellow, orange, red - shift colour more, by design, for evening and pre-sleep use, not daytime accuracy.
  • Colour shift tracks visible-light transmission: our 91.6% VLT clear lens stays near-true; deeper evening/pre-sleep tints shift more, by design.
  • Check the published transmittance report and wavelength band - a ‘blocks blue light’ percentage with no band is unverifiable.
  • ANSI Z80.3 covers light transmittance and colour, not reading-power accuracy - a pass says nothing about diopter precision.
  • A ‘clear’ lens can still filter roughly half the blue band; check the measured number, not the label.
  • Single-vision readers have one focal distance, don’t correct astigmatism, and are not a substitute for an eye exam.

​
How a filtered lens can shift colour

A blue-light filtering lens works by absorbing part of the visible spectrum, mostly at the blue end. Any wavelength that gets filtered changes what reaches the eye, so some colour shift is built into the category — the real question is how much, and that scales with how much visible light the lens lets through overall (its visible light transmission, or VLT) and how wide the filtered band is. A near-clear lens that filters mostly UV and a narrow sliver of blue reads close to true colour. Our clear lens, tested by COLTS Laboratories (report O-SPG111015, A2LA-accredited to ISO/IEC 17025), transmits 91.6% of visible light overall, filtering 99.99% at 400nm tapering to 33.1% at 450nm — heaviest right at the UV edge, lighter as the band moves toward visible blue. Evening and pre-sleep lenses are built the opposite way on purpose: our yellow evening lens filters 98% of the 400-500nm band at about 65% visible transmission, and the orange lens filters 99.96% across 380-500nm. Deeper filtering is the point at night, since it is what dims blue light before bed, and the visible colour shift that comes with it is a known tradeoff rather than a flaw.

​
The checks that work on any brand

Because colour shift scales with filtering, any blue-light reading lens — including ours — can be evaluated with the same handful of checks, using only what the manufacturer has published.
  • Ask for the transmittance report, not the marketing line. A credible one names the lab, the accreditation (ISO/IEC 17025 is the reference standard), and the test method. A percentage with no report behind it is a claim, not a measurement.
  • Read the VLT. This single number says how much visible light the lens lets through overall — the closer to 100%, the closer to true colour. A lens in the 60-70% range is a visible tint, whatever it is called.
  • Check the wavelength band, not just a headline percentage. ‘Blocks blue light’ with no band attached cannot be checked. A lens filtering 99% of a narrow slice near the UV edge is a very different product from one filtering 99% across the full 400-500nm blue range.
  • Do not assume ‘clear’ means minimal filtering. One of our own clear lenses (ZENOX) filters an average of about 52% across the 400-500nm blue band while filtering 100% of UV — a clear lens that is still doing meaningful filtering work. The name does not tell you that; the number does.
  • Match the lens colour to the data. A lab report can label a lens by its measured hue in ways that do not match how it is marketed — our own yellow evening lens is recorded as ‘amber’ on its COLTS report, which is why we call it yellow in copy rather than let the lab’s label stand uncorrected.

​
What an ANSI Z80.3 pass covers and what it leaves out

Our clear lens passed ANSI Z80.3 transmittance and chromaticity testing, on all samples in the tested group, filter category 0 (cosmetic lens) — a real, lab-run pass worth asking any brand to show. It means the lens’s colour and light transmittance were measured and met the standard’s tolerances, so colours read true rather than skewed by an uneven tint. What it does not cover is the reading power itself. ANSI Z80.3 is a transmittance and chromaticity standard; it says nothing about how accurately a lens is ground to its stated diopter. A lens can pass Z80.3 and still be off on magnification, because that simply is not what the test measures. Treat any claim that stretches an accredited transmittance pass into a statement about reading-power accuracy with suspicion — the two are separate tests, and the diopter-accuracy standard is a different one that we do not currently hold either.

​
Reading distance, screen distance, and the limits of a single-vision lens

A reading lens like this is single-vision: it has one focal distance, ground to the strength printed on the box. That focal point does not change when you move from a book, roughly 14-16 inches away, to a monitor, typically 20-28 inches away — the lens cannot refocus itself for both. Reading distance and screen distance are different distances, and any single-vision lens is a compromise at whichever one it is not tuned for. Choose the strength for the distance spent the most time at, rather than assuming one pair covers both equally well. None of this is a colour question, but it belongs in the same honesty check as the tint. A single-vision reading lens does not correct astigmatism, and no reading glasses, filtered or not, substitute for an eye exam. If print or a screen blurs, doubles, or strains at any distance, that is a signal for an optometrist, not a stronger over-the-counter diopter.

​
Comparing against a ready-made magnifier

None of these checks can be run on a ready-made magnifier, because that product class is not built around a published lab report — no transmittance data, no chromaticity pass, no wavelength band, because filtering blue light was never the design goal. That is the honest basis for comparison: not a price or a shop, but whether the product being compared can answer the same measurable questions at all. A lens with a report behind it can be checked, argued with, and held to a standard. One without a report is a piece of curved plastic with a strength stamped on the arm.

​
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.

​
A PROSPEK style for this

Buy on Amazon — $39.95

Ships from Amazon (Prime, 30-day returns). Sold by PROSPEK by Spektrum Glasses.