We address precision of estimation of the degree of polarization (DOP) from the orthogonal state contrast image (OSCI) in the presence of both signal-dependent Poisson noise due to useful signal. and additive Poisson noise due to dark current and / or background light. We determine the Cramer Rao Lower Bound and deduce from it figures of merit for DOP estimation. In particular. https://www.indiamapdigital.com/product-category/nail-biting/