Fig. 13 Wavelength discrimination of normals and dichromatic protanopes and deuteranopes. Over the entire spectrum these dichromats have inferior wavelength discrimination when compared with normals (also shown); dichromats have best wavelength discrimination in the region that appears blue–green to normals (approximately 495nm) and no wavelength discrimination for wavelengths beyond approximately 530 nm. Normals have best wavelength discrimination at approximately 490 nm and 590 nm.