Comparison of models 2 and 3 in relation to the residual of best fitted extinction parameter C(). Model 2 has been pre-corrected for a Gordon C = 1.00, and model 3 has been pre-corrected for a Calzetti C = 0.44. Ideally, the assumption of a pre-correction would be perfect if this procedure resulted in zero residuals, which is not the case. Simply, model 2 (green) is better because it has more zeros than model 3 (blue).