EBL scaling factor obtained for different redshift bins for FR17, GIL12, and DOM11 EBL models. Light colors refer to the statistical uncertainties, while darker colors include also the systematic ones. Comparison with (Ackermann et al. 2012) is also shown (gray). The shaded regions show the 1σ (dark gray) and 2σ (light gray) confidence intervals obtained for the whole sample, using the GIL12 EBL model and including both statistical and systematic uncertainties.