Difference between the [Fe/H] derived of the eight clusters (NGC 6791, NGC 6819, NGC 7789, M67, NGC 188, NGC 2420, NGC 2158, and M107, Mészáros et al. 2013), derived in this study with the reference value (see Table 2) as a function of the literature [Fe/H]. In addition, the Sun and Arcturus are shown as an orange star and red triangle, respectively. The blue and red dotted lines represent the [M/H] and [Fe/H] corrections, respectively, that are derived in Holtzman et al. (2015) for comparison.