The Gold Standard

ANOMALOSCOPE

This is how eye clinics settle red-green color vision for real. A circle is split in two: the top is a fixed yellow. The bottom you build yourself by mixing red and green. When the two halves become one seamless disc, you've made a match — and where you had to set the mix reveals how your red and green cones balance.

How it works

Mix red ↔ green (bottom)

Slide until the bottom's hue matches the yellow top.

Match the brightness (top)

Nudge the yellow's brightness until the seam between halves disappears.

Lock it — three times

Each round starts scrambled. Where you land, and how much you wander, is the result.

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Round 1 of 3 — make the two halves one solid disc.

Top: yellow referenceBottom: your mix

Bottom mix green ↔ red

Top brightness 50%

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Results

YOUR
RED-GREEN
MATCH

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Note

A real anomaloscope uses pure single-wavelength lights and careful calibration; a screen uses broadband RGB with unknown gamma, so this is a flavour of the instrument, not the instrument. It can suggest a protan (needed more red) or deutan (needed more green) lean and show a wide matching range, but a clean match here does not rule out a deficiency. Anything suggestive should be confirmed by a clinician. Not a diagnosis.

The anomaloscope is the clinical gold standard cited in OpticQuiz's published, open-access color-vision method — read the paper & open source →

About the anomaloscope test

The anomaloscope is the clinical gold standard for red-green color vision. You build the lower half of a split disc by mixing red and green light until it matches a fixed yellow reference — the classic Rayleigh match. Where you set the mix reveals how your red and green cones balance: needing extra red points toward a protan (red-weak) lean, extra green toward a deutan (green-weak) lean.

A real anomaloscope uses pure single-wavelength lights and careful calibration. A screen only has broadband red, green, and blue phosphors and no calibration, so this is a flavour of the instrument, not the instrument. It can suggest a lean and show a wide matching range, but a clean match here does not rule a deficiency out. Anything suggestive should be confirmed by a clinician.

Frequently asked questions

What is an anomaloscope?

A clinical instrument for red-green color vision. The subject mixes red and green light to match a yellow reference (the Rayleigh match); the settings they accept reveal the type and severity of any red-green deficiency.

Can a screen replace a real anomaloscope?

No. Screens use broadband RGB and aren't color-calibrated, so this is an approximation. It can hint at a protan or deutan lean but cannot diagnose or grade a deficiency.

What does needing more red or more green mean?

Protan (red-weak) observers perceive red as dimmer and tend to add more red to match. Deutan (green-weak) observers tend to add more green. A balanced match near the middle is typical of normal red-green vision.

Is this better than an Ishihara plate test?

It's a different tool. In clinic the anomaloscope grades red-green vision precisely; this screen version is a curiosity companion to plate tests, not a replacement for either.

ANOMALO­SCOPE

How it works

YOURRED-GREENMATCH

About the anomaloscope test

Frequently asked questions

ANOMALOSCOPE

YOUR
RED-GREEN
MATCH