A new method is proposed to generate transversely coherent energetic photon beams. It does not rely on stimulated photon emission, therefore, is not subject to the same technological and cost limitations which affect bound‐state x‐ray lasers and free‐electron x‐ray lasers. The method leaves unchanged the photon source; it increases transverse coherence by dynamical optical means, i.e., using nonstationary optical elements. It is well suited to first‐order interference experiments (e.g., x‐ray holography) particularly with synchrotron radiation sources.