We review the equations determining the photon sphere radius and the black hole shadow radius, and calculate the cosmological constant corrections arising when the dark energy action has the usual form, and when dark energy arises from a Weyl scaling invariant dark energy action. For black hole targets of the Event Horizon Telescope, the corrections are very small.
@article{arxiv.2205.04628,
title = {Cosmological constant corrections to the photon sphere and black hole shadow radii},
author = {Stephen L. Adler and K. S. Virbhadra},
journal= {arXiv preprint arXiv:2205.04628},
year = {2023}
}