Figure showing the Mueller PRM M_coro for the TMT in I-band to show how polarization shapes the PSF. A simple imager would observe the I → I component of M_coro. The data shown here are normalized to the peak of this component. In response to unpolarized light, the observed image of a point-source is simply the sum of the top row times the Stokes vector that represents the source. However, for images that we detect in linear polarized light the U → Q and Q → U retardance terms may sculpt the disk image in a way that inhibits precise detection. The data here is plotted with a colorbar such that bright signals are saturated to enhance the structure in the first lobe of the PRM elements.