Standard sets of metamers are used to test day-light simulators intended for visual appraisal or measurement of color. A new set is proposed and a method is given for evaluating the sensitivity of test metamers to various spectral defects in the visible spectrum. Ideal illuminant spectra were perturbed in specified ways to find the amount of defect tolerated without exceeding a given standard quality category. The amount of perturbation was compared to that tolerated by existing standard metamers, to assure that new metamers grade simulators on the same internationally accepted scale of quality. The method was used to validate metamers designed to assess simulators of CIE Illuminant D50, over the spectral range 400-700 nm, and new metamers designed To assess simulators of CIE Illuminants D50, D55, D65, and D75, over the spectral range 380-780 nm.