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The behaviors of null geodesics in the spherical symmetric black holes inEinstein-Maxwell-dilaton (EMD) theory with coupling function$f(\Phi)=e^{-2\alpha \Phi}$ are meticulously analyzed. We investigate theeffects of coupling constant $\alpha$ on the effective potential of photontrajectories within three ranges, namely $0<\alpha <1$, $\alpha =1$ and $\alpha>1$. We find that the thicknesses of lensing and photon rings are smaller atlarger $\alpha$ and fixed electric charge in the unit of mass $q$, whereas theyare larger at fixed $\alpha$ and larger $q$. Remarkably, the behaviors ofphoton trajectories are found to be more interesting when $\alpha>1$. Namely,the radius of the black hole shadow $R_\text{s}$ becomes to be smaller than thephoton sphere radius $r_\text{ph}$ when $\alpha > 1$ and $q>q^*$. Moreover,$R_\text{s}$ goes to zero as $q$ saturates the extremal limit, beyond which thephoton orbit becomes absent. %This tends to be consistent with the result ofWilczek. Furthermore, we construct the optical appearance of black holessurrounded by optically and geometrically thin accretion disks with threeemission models. Our results indicate that the observed flux originating fromthe lensing and photon rings exhibits suppression as $\alpha$ increases, whileit undergoes amplification with the increasing parameter $q$.

Remarks on the light ring images and the optical appearance of hairy black holes in Einstein-Maxwell-dilaton gravity