FWHM as a function of wavelength for the three different templates, panel a) Indo-US, panel b) MARCS, and panel c) ELODIE v.3.1 library. Different colours identify the MILES library (blue), the subsample of MILES stars with solar metallicity (red), the subsample of MILES stars in common with either Indo-US or ELODIE (orange), the MILES SSP from Maraston & Strömbäck (2011) (green). The dashed line represents the nominal FWHM = 2.3 Å (Sánchez-Blázquez et al. 2006), whereas the dotted-dashed line represents the median of the FWHM obtained here. In the first wavelength bin of panel a) and b) the FWHM of SSP are not shown because out from the FWHM range (see Maraston & Stromback for details).