The relative spectral sensitivity was measured at luminance levels ranging from scotopic to near photopic vision. This was done for various photometric field sizes of 3 to 64 degrees in diameter. The spectral absorption of the macular pigment seems to account for the difference in the blue part of the spectrum occurring between small and larger fields. The influence of the field size in mesopic levels depends on the spectral region. In order to define the mesopic standard observer, the Commission Internationale de l'Eclairage (CIE) has suggested a set of curves which were partly based on experiments obtained under different conditions. It could be shown that these curves nearly coincide with those obtained with the 64 degrees field. The V10 degrees(lambda) curve derived from color equation measurements could be confirmed as a luminance efficiency curve obtained by direct brightness match measurements.