The Rayleigh match test is a classic method used to study color vision by mixing red and green light to match a monochromatic orange light. Among people with normal color vision, there is variability in sensitivity to red light, often related to differences in the properties of cone photopigments, particularly the long-wavelength (L) cones.

Factors Explaining Variation in Red Sensitivity

• Long-wave cone pigment variations: Differences in the L-cone pigment’s amino acid sequence and structure lead to slight shifts in the absorption spectrum (peak wavelength shifts by a few nanometers).

• Peak sensitivity differences: For example, in red-sensitive individuals, the absorption peak of L-cone pigment may be around 556 nm, versus around 552 nm in others.pmc.ncbi.nlm.nih

• Opsin protein structure: Changes in the primary structure of the long-wave opsin protein can account for sensitivity shifts, influencing color perception.pmc.ncbi.nlm.nih

Evaluating the Statements

• (1) Variations in sensitivity of long-wave cone pigments: True, explaining red sensitivity variability.

• (2) Short-wave cone opsin differs in red-sensitive subjects: False; red sensitivity differences are linked to long-wave cones (L cones), while short-wave (S) cones are responsible for blue vision and are not typically implicated in red-green sensitivity.

• (3) Absorption peak differences of L-cone pigment (556 nm vs 552 nm): True.

• (4) Primary structure variation of long-wave opsin in red-sensitive subjects: True.

Therefore, the incorrect statement is:

(2) The short-wave cone opsin in red-sensitive subjects is different from others.

Conclusion

Red sensitivity variation in normal color vision is primarily due to differences in the long-wave cone opsin, not the short-wave cone opsin. This explains the variation in Rayleigh match outcomes observed in normal individuals.