For a protanope, is the Copunctal point closer to 400nm or 700nm?

For a protanope, the Copunctal point is associated with the absence of the long-wavelength sensitive cone photopigment, which primarily affects color perception towards the red end of the spectrum. In the context of color vision, the Copunctal point is where the chromatic confusion occurs, indicating how certain wavelengths appear equivalent to the individual when perceived through their unique color deficiencies.

In protanopes, due to the lack of responsiveness to red light, their perception will be skewed away from longer wavelengths. The Copunctal point will therefore align more closely with longer wavelengths in the spectrum due to the absence of the long-wavelength cones. Thus, it is positioned nearer to 700 nm than to 400 nm, making the choice of 700 nm the accurate answer. This position reflects the color confusion experienced by individuals with protanopia, leading to a greater mix-up and overlap in their visual perception of color as it leans more towards the spectral extremes.

Understanding the Copunctal point in this context allows for better insight into how individuals with specific color vision deficiencies perceive colors differently compared to individuals with normal color vision.