Estimation of luminance factor from cie supplementary standard colorimetric observers

The luminance or luminance factor is not defined in the large viewing field greater than 4° since the color matching function ?₁₀(Λ) is not identical to the spectral luminous efficiency V(Λ). the possible errors are estimated when ?₁₀ (Λ) is used in place of V(Λ) for evaluating the luminance factor.