Most blue-light glasses come with a claim and nothing else. “Blocks 100% of blue light.” “Filters harmful rays.” A number, printed on a box, with no report behind it.
If you are comparing lenses before purchasing, start with our guide to choosing the best blue-light glasses, then use the framework below to assess the test data behind each claim.
The more useful evidence is a transmittance report. It contains percentages and a curve showing how a lens performs across different wavelengths.
Here is how to read one.
Three things matter, not one number
A lens transmittance report has three main components:
- Transmittance (%) — how much light passes through the lens at a given wavelength. A lower percentage means less light is transmitted at that point.
- Wavelength (nm) — the position on the light spectrum being measured. Blue-violet light is generally discussed across the lower end of the visible spectrum, around 400–450 nanometres.
- The curve — how transmittance changes across the full measured range, rather than at one isolated wavelength.
Many marketing claims highlight one percentage at one wavelength. A complete report shows the wider curve.
Why “100% blocked at 400 nm” does not tell the whole story
This is a common claim, and it may be technically accurate. Many lenses can show extremely low or zero transmittance at 400 nanometres.
However, 400 nm sits at the lower edge of the visible spectrum, close to ultraviolet light. The more useful question is how the lens performs as the wavelength rises through the rest of the blue-violet range.
Two lenses can both advertise strong filtration at 400 nm while performing very differently between 410 nm and 450 nm. A single percentage cannot show that difference. A spectral curve can.
What a transmittance curve shows
A tested lens report may plot transmittance at regular intervals across the visible spectrum and beyond. Reading the graph from left to right shows how much light passes through the lens as the wavelength increases.
A selectively filtering lens may show lower transmittance at shorter blue-violet wavelengths, followed by a gradual rise as it moves through the visible spectrum.
A rising curve is not necessarily a flaw. It can show that the lens is filtering more strongly at one part of the spectrum while allowing more visible light through at higher wavelengths.
This selective approach is particularly relevant for people looking for blue-light glasses without a heavy yellow tint, including designers, photographers and other professionals whose work depends on natural-looking screen colour.
Our own numbers, shown plainly
CLÆR SPECTRUM™ lenses were lab tested to ISO 12312-1:2022 and ANSI Z80.3-2018.
You can see the full filtration profile and supporting information on our Technology page.
At 400 nm, the report records 0.00% transmittance. At 420 nm, transmittance is approximately 22%. At 450 nm, it reaches 93.83%. Overall visible-light transmittance is recorded at 90.35%, while UVA and UVB transmittance are both reported at 0.00%.
Across the raw measurements from 400 nm to 450 nm, the average filtration is approximately 55%. This is the figure shown on our Technology page. It represents an average across the measured range rather than a single selected wavelength.
Read the curve yourself
You do not need to rely on a single headline percentage. Look for a complete report that shows how the lens performs across a meaningful wavelength range.
We would rather you understood the data than simply trusted the claim. For more context on how selective filtration can affect lens appearance, read what the CLÆR lens test shows about clearer-looking blue-light lenses.
See the lens in everyday eyewear
CLÆR SPECTRUM™ lenses are used across the PROJECT CLÆR First Edition, combining selective blue-violet filtration with more natural-looking screen colour and hand-finished acetate frames.
Explore PROJECT CLÆR blue-light glasses, or discover our stylish blue-light glasses designed for screen-heavy working days.
Blue-light lens reports: quick answers
What is a blue-light lens transmittance report?
It is a laboratory report showing how much light passes through a lens at different wavelengths. Lower transmittance means less light passes through at that wavelength.
Why is one filtration percentage not enough?
A single percentage may refer to only one wavelength. A complete spectral curve shows how the lens performs across a wider measured range.
What does wavelength mean in a lens report?
Wavelength is measured in nanometres. Blue-violet light sits toward the shorter end of the visible spectrum, commonly discussed around 400–450 nm.
Does a clear blue-light lens still have some tint?
A lens that filters visible blue-violet light can have a subtle tint off-screen. The important question is how noticeable the colour shift is during normal screen use.
Where can I see the PROJECT CLÆR test data?
The CLÆR SPECTRUM™ transmittance profile and technical information are available on our Technology page.
