What is the only approved lighting for color vision testing?

The only approved lighting for color vision testing is Standard Illuminant C. This illuminant is based on daylight, specifically the average daylight or the CIE standard daylight illuminant, which has a color temperature of approximately 6500K.

Using this standardized lighting is critical because it provides a consistent and neutral reference for assessing color discrimination. The spectral power distribution of Standard Illuminant C closely mimics natural daylight, allowing individuals to perceive colors as they would in natural conditions. This consistency is vital for accurately determining whether a person's color vision is normal or if there are deficiencies.

On the other hand, the other illuminants (A, B, and D) have different spectral compositions and color temperatures, which may alter the appearance of colors being tested. For example, Standard Illuminant A represents tungsten light with a warm tone, while Standard Illuminant B is less commonly utilized and does not align with the needs of color vision testing. Due to these variations in lighting conditions, they are not suitable for reliable color vision assessments.