The rest-frame ultraviolet spectral region for different stellar population models with an identical luminosity at 1500 Å. Binary population synthesis models are compared to single-star models, for either an instantaneous starburst or continuous star formation rate of 1 M_⊙ yr⁻¹, at age of 100 Myr. The stellar mass of the continuous starburst models is 10^6.0 M_⊙, while that of the starbursts is 10^6.9 M_⊙. A stellar metallicity of Z = 0.002 is shown.