We consider the reconstruction of the electric permittivity and conductivity of a medium from far-field measurements of scattered time-harmonic electromagnetic waves. We will present ogarithmic conditional stability estimates for this problem with an explicit exponent and the $L^2$-norm for the far-field patterns. Moreover, we discuss the numerical solution of this problem by a preconditioned, regularized Newton method and the implications of the stability result for the convergence of the reconstruction method. The performance of this method is illustrated in numerical examples.