Which chromaticity point is closest to 700 nm for protanopes?

The co-punctal point is closest to 700 nm for protanopes because it represents the wavelength at which the sensitivity of the longer-wavelength cones (red cones) aligns with the sensitivity of the other photoreceptors in the absence of those red cones due to the dichromatic nature of protanopia. Protanopes have a deficient response to the longer wavelengths of light, leading to a shift in their chromaticity point.

The co-punctal point essentially indicates the ideal mixing of light wavelengths to produce an equivalent color experience for protanopes, particularly near the red spectrum, where they would otherwise experience difficulty. This point is important for understanding how individuals with protanopia perceive colors and where their sensitivity is maximally aligned despite the absence of certain cones.

Other options like desaturation point, convergence point, and color blindness point do not specifically pertain to the accurate chromaticity representation for the protanopic perception near the 700 nm region. They may represent other aspects of color vision or different types of color deficiency but do not precisely indicate the point of maximum sensitivity or equivalence for protanopes in relation to longer wavelengths.