Farnsworth D-15 Test Online

What the Farnsworth D-15 test actually measures

Dean Farnsworth published the dichotomous D-15 in 1947 as a short arrangement test. You start from a fixed pilot cap and place 15 remaining caps in the order that looks like the smoothest hue run. People with typical colour vision walk around the hue circle. People with a significant colour vision deficiency jump across it—those jumps are the major crossings drawn in red on the score plot.

Unlike an Ishihara plate test, D-15 is not primarily a “is CVD present?” screen. It is a classification task: the direction of crossings can suggest protan (red), deutan (green), or tritan (blue-yellow) confusion, and a clean circle usually means normal or very mild deficiency.

How to take this online D-15

1. Use a bright screen. Turn off Night Shift, Extra Dim, and blue-light filters.
2. Sit at a normal reading distance. Do not squint at a tiny phone in the dark.
3. Sort by hue, not by how light or dark a cap looks.
4. There is no time limit. When the run looks smooth, score it.

This browser version uses evenly spaced HSL hues, not calibrated Munsell papers under Illuminant C. Absolute pass/fail will shift with your panel. The pattern of crossings is still the useful part of the exercise.

How scoring works (clinic vs this page)

On a score sheet, each cap has a fixed place on a hue circle. Adjacent caps in a normal order sit next to each other on that rim. A major error is a line that cuts across the circle. Many clinics treat more than two major crossings as a fail. Software scoring often uses Vingrys & King-Smith (1988): a confusion index (1.0 = perfect) and a confusion angle (type).

DeficiencyView counts those crossings and reports the axis that the jumps resemble most. We do not output a clinical confusion index. Confirm anything that matters for work or licensing with a calibrated exam—see color vision tests for jobs.

Example crossing patterns

These diagrams are teaching sketches of the three confusion axes. Real arrangements are messier. Red chords = crossings.

D-15 vs Ishihara vs FM-100

• Ishihara-style plates — fastest red-green screen; better for mild deuteranomaly.
• D-15 — short arrangement; type hint; mild CVD often still passes.
• Farnsworth–Munsell 100 Hue — ~85 caps, Total Error Score, finer discrimination, 8–12 minutes.

FAQ

What is the Farnsworth D-15 test?

The Farnsworth D-15 (dichotomous test, 1947) is a hue-arrangement exam: you order 15 Munsell caps from a fixed pilot. Error chords across the hue circle can suggest a protan, deutan, or tritan confusion axis and separate significant deficiency from a pass.

Is this online D-15 the same as a clinic test?

No. Clinics use physical Munsell caps under a standard illuminant. This page approximates hues in HSL on your uncalibrated display. Treat it as practice / screening, not a diagnosis or occupational certificate.

How is the D-15 scored?

The classic Farnsworth method counts major crossings—jumps that cut across the hue circle instead of stepping to a neighbour. Clinics often treat more than two major crossings as a fail. Quantitative software may instead use the Vingrys & King-Smith (1988) moment-of-inertia method (confusion index and angle). Our browser screen counts those crossings and guesses an axis; it does not compute a clinical confusion index.

D-15 vs Ishihara — which should I take?

Ishihara plates are more sensitive for mild red-green screening. D-15 is a classification task: it often misses mild deuteranomaly, but error direction can hint at type, including tritan. Take plates first, then D-15 if you want an arrangement picture.

Can a D-15 pass help me get a job?

A clinical D-15 is named in some occupational standards. An online pass or fail does not certify you. Read the jobs guide before treating any browser score as documentation.

Can the D-15 detect mild color blindness?

Not reliably. The dichotomous D-15 is built to split significant deficiency from normal or very mild vision. Mild anomalous trichromacy often still arranges the caps well. Use Ishihara or HRR-style plates to screen for mild red-green CVD.