The Other Axis

CONTRAST
SENSITIVITY
TEST

Eye charts test sharpness with high-contrast black letters. But real life is full of faint differences — fog, dusk, a face across a dim room. This test fades a letter toward the background until it nearly vanishes, and finds the faintest one you can still read. It's a different axis of vision entirely, and often the first to slip.

How it works

1
Name the letter
One of six shows faintly. Tap which one — or "Can't tell" if it's gone.
2
It fades as you succeed
Get it right and the next is fainter; miss and it strengthens. This finds your edge.
3
Sit back a little
Arm's length, screen brightness up. ~24 trials.
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TRIAL 1 / 24—

Which letter do you see?

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Results

YOUR
CONTRAST
FLOOR

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Note
Contrast sensitivity is a genuinely useful axis — it can dip before sharpness does in some eye conditions. But your screen's brightness and gamma are unknown and uncalibrated, so this is not a Pelli-Robson score and can't be compared between devices. It's most meaningful tracked against your own results on the same screen. There is also a hard floor: an 8-bit display can only step luminance so finely, and that smallest step is about 8% near black and 0.9% near white, so the faintest letter this page can draw depends on how bright its background is. This test stops at that floor rather than pretending to go below it, and tells you when your result landed there. A real contrast test is done by an eye clinic. Not a diagnosis.