A normal trichromat sets the mixture scale to approximately what value on the Nagel Anomaloscope to achieve a match?

In the context of color vision testing using a Nagel Anomaloscope, a normal trichromat typically has a balanced sensitivity to the three primary colors: red, green, and blue. The anomaloscope is designed to assess color discrimination and match by adjusting the mixture of these colors.

For a normal trichromat, setting the mixture scale to approximately 45 is indicative of the point where the perceived balance between the red and green components aligns with the color of the test light, allowing for an accurate match. This value reflects the normal physiological response to color under standard conditions without any color vision deficiencies.

Understanding the mechanics of the Nagel Anomaloscope, the value of 45 corresponds to a specific mixture ratio that is representative of a typical response from someone who has no deficiency in their color vision capabilities. The other choices do not align with the typical setting for a normal trichromat, as they indicate ratios that would be either too low or too high for someone with standard color perception. Thus, the selected value serves as a benchmark for assessing and diagnosing color vision performance.