Comparison of line profiles for a Keplerian disc, calculated considering only relativistic Doppler shifts as outlined in section 2.5 (solid coloured lines) and calculated using the DISKLINE model (Fabian et al. 1989) (dashed lines), which includes some corrections expected from the Schwarzchild metric. In all cases these are calculated for a narrow annulus, such that r_out = 1.1r_in. The left panel shows the profiles while stepping through values of r_in, in order to highlight where our approximations break down. For r_in ≳ 50 our line profile matches that or DISKLINE well, whereas below this we start to see systematic offsets originating from our choice of metric. The middle and right panels show the profiles while stepping through observed inclination, with r_in = 20 and 200 respectively. Again, in the weak field limit, where general relativistic corrections are small, our approximation matches well that of DISKLINE.