Journal / 02
What 480 nanometres actually means
Every pair of blue-light glasses quotes a number. Here is what ours means, with the measured curve printed rather than described.
Light is a spectrum, measured in nanometres
Visible light runs from roughly 380 to 700 nanometres. The short end reads as violet and blue. The long end reads as orange and red. Every lamp and every screen is a mix across that range.
When a lens is described as filtering blue light, the only honest questions are: which part of the range, and how much of it.
Where this lens draws the line
The cut-off sits at about 480 nanometres. Below it, the lens absorbs almost everything. Above roughly 500 nanometres it is nearly open, so the rest of the spectrum arrives intact.
That is the whole design decision, and it is why the lens is visibly amber rather than clear.
- < 1 %
passes below 450 nm
The deepest blue — the part screens and LEDs push hardest.
- ≈ 480 nm
cut-off
Where the lens stops blocking and starts letting light through.
- ~ 62 %
visible light
The room stays bright enough to read, cook and work in.
Reading the curve
Follow the line from the left. It sits on the floor through the deep blue — under 1% passes below 450 nm. At 480 nm it climbs steeply. Past 500 nm it flattens out near the top and stays there.
The shaded area on the left is the light that does not reach your eyes. Everything to the right of the rise does.
Why not block everything
Because you still have to see. Around 62% of visible light passes, which is enough to read, cook, work and move around a room normally.
A lens that blocked more would be darker, not better. This one is built for a room with the lamps on, not for a darkroom.
What we do not claim
These figures are manufacturer spectral data for this lens batch, not an independent laboratory report, and we say so on the product page too. If that changes, the label changes with it.
We also make no medical or sleep promises. What we can show is what the glass does to light. The rest is your evening.
A number is only a claim until you publish the curve behind it.
What this means for you
- Cut-off ≈ 480 nm: below it the lens absorbs, above it it lets light through.
- Under 1% passes below 450 nm — the deepest blue screens push hardest.
- About 62% of visible light still passes, so the room stays usable.