Farnsworth Lantern Test: What It Checks and What It Cannot Confirm

What the lantern asks you to do

The National Research Council’s 1981 review describes nine vertical pairs of red, green, and white lights that the observer names. It frames lantern tests as practical occupational tasks whose value depends on the work condition being simulated (National Academies, Procedures for Testing Color Vision).

A lantern result does not describe every kind of color discrimination. For one red-green type, see protanopia. “Farnsworth Lantern” names a particular instrument and procedure, not every web page that flashes colored circles.

Four tests, four different tasks

This is a task map, not a ranking of accuracy or an occupational recommendation; each row links to the source for its description.

The National Eye Institute’s December 6, 2024 page describes a plate task as finding a dotted figure and a hue task as ordering colored blocks (NEI).

The 2021 D-15 instructions and X-Rite’s product materials both specify controlled daylight conditions for their physical cap tests. Those are instructions for those instruments, not settings that this page can reproduce on your screen.

Online practice and official assessment are separate steps

An RGB page and a physical instrument use different presentations, so the screen activity cannot reproduce the instrument procedure.

The eCFR text current through August 10, 2026 lists the Farnsworth Lantern among accepted methods for the specific U.S. Coast Guard deck-credential color-sense determination. That rule does not establish acceptance by an airline, railroad, employer, or another authority (46 CFR § 10.305).

In Cole and Maddocks’ 2008 study, 52 participants with color deficiency and 52 with normal color vision named simulated PAPI lights under two visibility conditions; the 10 participants with color deficiency who passed FALANT still made more PAPI errors than the normal-vision group (Cole and Maddocks, 2008).

If an application or medical examiner names FALANT, ask which actual procedure is required, who administers it, and which authority’s criteria apply. Do not substitute this guide, a browser activity, or a different color test for that instruction.

Keep the two records from becoming one

Use this card to preserve what happened without turning a practice result into an occupational decision. Keep an online activity in its own line and a clinic or employer-administered test in a separate line. Create a fresh entry when the method changes instead of overwriting an earlier result.

1. Write the exact test name shown by the provider or page, including any version or model the provider identifies.
2. Mark whether the activity used a browser screen or a physical instrument.
3. For a formal assessment, record the date and the administering provider as stated on the report.
4. Copy the result wording exactly, including any stated criterion or follow-up instruction.
5. Note the purpose of the assessment, such as a personal question or a named application requirement.
6. Keep the source of each line beside it so a later reader can tell which result came from which procedure.
7. If a report states the number of runs or a retest, copy that wording without converting it into another test’s score.
8. Leave a field blank when the provider did not give that information; do not infer a threshold from a different test.
9. Store the provider’s report with the entry when you have one, so the short note can be checked against its source.
10. If a later appointment uses another method, add a new entry and preserve the earlier wording.
11. When sharing a note, include the method label beside the result rather than sending the number alone.
12. Use the questions field to ask which method is accepted, who must administer it, and where the written criterion comes from.

For a provider visit, bring the wording rather than a self-assigned label. The National Eye Institute advises people with color-vision concerns to talk with an eye doctor, who can choose tests and interpret unclear results (NEI).

A note that says “screen exercise” should remain separate from one that names the instrument used in a formal assessment. That separation lets you trace a saved note back to the procedure it describes.

What this page can and cannot answer

This page can help you recognize the signal-light task, compare it with plate and cap-arrangement formats, and carry a clear record into a conversation with a qualified examiner. It cannot tell you which result an employer will accept or whether you meet a personal medical standard.

If you need a formal assessment, ask the organization that requested it for the accepted method and arrange testing with its qualified provider. Use the saved note to ask about the exact instrument and interpretation, not to predict the outcome.