QED effect on a black hole shadow

Taking QED effect into account, we investigate the shadows of a static black hole with magnetic monopoles and neutral black holes in magnetic fields through the numerical backward ray-tracing method. For a static black holes with a magnetic monopole, we obtain the relation between the shadow radius and the coupling constant. For neutral black holes in uniform magnetic fields, we find that the shadow curves deviate very little from the ellipses for an equatorial observer, and we read the linear relation between the eccentricity and the coupling constant. For θo ≠ π/2, we find that the shadow curves can be well approximated by ellipses in most cases, except when the magnetic field is very strong and the observer sits around the angle θo = π/4 or 3π/4 . Moreover, we extend our investigation to a neutral static black hole surrounded by a current loop.