The Farnsworth Lantern Test is a test of color vision. Test takers must identify the colors of two lights that may be any combination of red, green or white.
Test takers view a series of nine color combinations. These color combinations may be two different colors or two of the same color. To pass the test, applicants must correctly identify at least eight out of the nine color combinations. The colors are only shown for two seconds, as it is possible for those without color vision to eventually discern the difference from luminance cues. The test is designed so that those with mild color-vision deficiency can still pass it.
The test is commonly abbreviated as FALANT and is used by the U.S. military for color-vision testing. FAA authorization is not required to take this test, so it is usually the first option employed in flight testing. Military test-takers who pass the exam do not have a color or night-flying restriction. Those that do not pass the exam have the option of taking a color signal light test, operational color vision test or a color vision medical flight test as alternative evidence of color vision. These tests may require authorization from the FAA.