Effect of choice of optical constants demonstrated on example model SEDs for pure and mixed compositions, and grain sizes of 0.01, 0.1, 1.0 and 5.0µm. SEDs are plotted for all combinations of four sets of carbon and four sets of silicate optical constants, resulting in four SEDs in each panel for pure composition, and 16 for the mixed compositions. The fixed parameters of the model are M_d =3.4×10⁻⁴M_⊙, R_out=1.21×10¹⁷cm, T_* = 7097K, and L_* =1.53×10⁸L_⊙.