Color Vision Tests Compared — Ishihara, HRR, Anomaloscope, D-15, FM-100
The difference between screening and diagnostic tests, and a table comparing what pseudoisochromatic plates, arrangement tests, the anomaloscope, and computerized tests each reveal — and their limits.
Color vision tests fall broadly into screening (quickly flagging whether a deficiency exists), classification (which type), and grading (how severe). No single test does all three well, so clinics combine tests depending on the purpose.
At a glance
| Test | Method | What it's good at | Limitations |
|---|---|---|---|
| Ishihara | Reading numbers on dot plates (pseudoisochromatic) | Screening for red-green deficiency | Doesn't test blue-yellow; limited grading |
| HRR | Symbols on dot plates (circle, cross, triangle) | Red-green and blue-yellow screening with rough grading | Limited accuracy in separating protan from deutan |
| Anomaloscope | Matching a red + green light mixture to yellow (Rayleigh match) | Separating protan from deutan; dichromacy vs. anomalous trichromacy | Requires equipment and a skilled examiner |
| Farnsworth D-15 | Arranging 15 color caps in hue order | Whether the deficiency is moderate or worse, and its axis (type) | Mild deficiencies often pass |
| FM-100 Hue | Arranging 85 color caps | Color discrimination score; tracking acquired changes | Time-consuming |
| Computerized tests (CCT, etc.) | Finding the orientation of a target in luminance noise | Discrimination thresholds per axis | Requires a calibrated monitor and setup |
| Lantern tests | Naming the colors of small signal lights | Real-world signal recognition (occupational) | Standards vary by organization |
Pseudoisochromatic plates — Ishihara and HRR
Since its first publication in 1917, the Ishihara test has become the most widely used screening test in the world. It excels at quickly catching red-green deficiency, but the standard edition does not test blue-yellow vision. HRR (Hardy-Rand-Rittler) uses symbols instead of numbers and includes blue-yellow plates, giving it a wider screening range and a rough indication of severity.
Colorblind Lab's check uses the same principle (color pairs on confusion lines) but adds luminance noise and generates fresh plates every time. Its purpose stops at screening and estimating a tendency.
The anomaloscope — the diagnostic standard
In this test, the observer mixes red and green light until it looks the same as a neighboring yellow light. People with normal color vision make a match only within a narrow range of mixing ratios, but protan defects need more red and deutan defects more green, while dichromats accept a match at almost any ratio. That's why it serves as the standard test for determining the type and for separating dichromacy from anomalous trichromacy.
Arrangement tests — D-15 and FM-100
These tests have you line up color caps in hue order. The direction in which misplaced caps jump across the hue circle (the confusion axis) suggests the type. The D-15 is used to judge whether a deficiency is “significant enough to matter in daily life,” and the FM-100 scores fine discrimination to track acquired changes caused by eye disease or medication.
Which test should you take?
- If you're simply curious: a pseudoisochromatic plate test at an eye clinic is enough.
- If you need your exact type and severity (for occupational standards, etc.): it's best to take an anomaloscope test together with an arrangement test.
- If your color discrimination has changed recently: it may not be congenital, so see an eye doctor first.
An online check replaces none of these. But as a first step in deciding “Should I get tested?” it's genuinely useful.