Although the CIE states that the 1931 2 degrees [(x) over bar(lambda), (y) over bar(lambda), (z) over bar(lambda)] standard observer characteristics and those of the 1964 10 degrees [<(x(10))over bar>(lambda), <(y(10))over bar>(lambda), <(z(10))over bar>(lambda)] standard observer were derived from experimental data in the same way, there are differences. One discrepancy is a difference of 6 nm in the tangent wavelength of the (Y)(Z) line on the chromaticity chart with a corresponding change in the minimum wavelength of <(x(10))over bar>. The reason for this is investigated and the two systems are considered.