An investigation was carried out to study the neutral white of chromatic adaptation in colour science. The experiment was conducted for matching neutral whites under different white illuminants using both surface and self-luminous colours to collect data of the neutral whites of human vison under different illuminants (adaptation fields). The result proves the previous study about the chromatic adaptation. Not all the white illuminants are found neutral even the adaptation time is long enough. The baseline illuminant of the 2-step CAT was found as the illuminant with the same chromaticity of the neutral white under it. The results were also used to test models of the effective degree of chromatic adaptation, which was found highly associated with the viewing media in the present study.