Energy shift, g, of photons propagating from off-axis sources, located at h = 3r_g, at two ring radii x = 2r_g (blue lines) and x = 5r_g (red lines), and BH spin of a = 0.998. Photon trajectories are selected from an isotropic distribution of the initial photon directions in the rest frame of the sources. Lighter lines show energy shifts of photons emitted by the off-axis sources located on the same ring at different azimuthal angles. Thick lines represent the resulting averaged energy shifts over the disk annuli. The dashed black line corresponds to the energy shift of the photons from a lamp post source with h = 3r_g.