 Abstract semiconductor excitations can hybridize with cavity photons to form exciton polaritons, EPS, which have unique properties such as light-like energy flow combined with matter-like interactions. These EPS are difficult to study due to their complex interactions with lattice phonons, but recent advances in imaging techniques allow researchers to observe them in real space. In this paper, the authors developed a non-linear momentum-resolved optical approach to image EPS in lead halide perovskite microcavities. They found that EP phonon interactions cause a significant renormalization of EP velocities at high excitonic fractions while maintaining ballistic transport at lower fractions. The authors also simulated the effects of dynamic disorder shielding by light-matter hybridization, finding that it protects against decoherence above 50% excitonic character. This work provides a general framework to optimize EP coherence, velocity, and non-linear interactions. This article was authored by Ding Xu, Akajit Mundal, James M. Baxter, and others.