It might be valuable to more explicitly define half-light radius and scale radius, i.e., ```I(r) propto exp[-(r/r0)^(1/n)]``` vs. ```exp[-b_n (r/r_{1/2})^(1/n)]```, where b_n is implicitly defined by the condition ```\int_{0}^{r_{1/2}} I(r) 2pi r dr = 0.5 \int_{0}^{infinity} I(r) 2pi r dr```.