  The mean ($\kappa$) and Gaussian ($\bar{\kappa}$) bending rigidities of
liquid-liquid interfaces, of importance for shape fluctuations and topology of
interfaces, respectively, are not yet established: even their signs are
debated. Using the Scheutjens Fleer variant of the self-consistent field
theory, we implemented a model for a symmetric L/L interface and obtained high
precision (mean field) results in the grand canonical $(\mu, V, T)$-ensemble.
We report positive values for both moduli when the system is close to critical
where the rigidities show the same scaling behavior as the interfacial tension
$\gamma$. At strong segregation, when the interfacial width becomes of the
order of the segment size, $\bar{\kappa}$ turns negative. The length scale
$\lambda \equiv \sqrt{\kappa/\gamma}$ is of order the segment size for all
strengths of interaction; yet the $1/\sqrt{N}$ chain length correction reduces
$\lambda$ significantly when the chain length $N$ is small.
