Comparison between the data of Illustris-1 and Illustris-TNG100. The black lines mark the TNG data, while the red ones the Illustris-1 data. The solid line refers to the data at z = 0, while the dashed lines to the data at z = 4. From top left to bottom right we show: the effective radius R_e (enclosing half the total luminosity or half the total stellar mass (for TNG); the effective surface brightness I_e; the central star velocity dispersion σ; the stellar mass-to-light ratio (M^*/L); the total luminosity (in solar units); and the total stellar mass (in solar units).