The relative spectral response of the lux meter should ideally be the same degree of brightness as V(λ), which is the unit of brightness to which human beings are considered sensitive.

In the JIS standard, the system of evaluating the characteristics of the visible region relative spectral response is adopted in order to bring the relative spectral response of the lux meter much closer to this ideal. 

The 510 series lux meter measures the intensity of illumination more accurately because its sensitivity approximates to the standard spectral luminous efficiency which is the same sensitivity as the human eye.

However, since spectral characteristics differ depending on the light source types, a subtle indication error occurs.