Optical appearance of numerical black hole solutions in higher derivative gravity Yu-Hao Cui, Sen Guo, Yu-Xiang Huang, Yu Liang and Kai Lin Eur. Phys. J. C, 84 8 (2024) 772 Published online: 03 August 2024 DOI: 10.1140/epjc/s10052-024-13153-2