Comparisons between the σ-type 5780 Å DIB EW and the UV bump height, under formalism 1 of the extinction law (a-c) and formalism 2 (d-f). Data are from the compilation of Xiang et al. (2017). (a) and (d) show the bump height vs the reddening-normalized EW for all targets and the adjusted linear fit. The colour-coding refers to the extinction (from yellow for the lowest extinctions to black for the highest ones). Errors bars on EWs are indicated. (b and e) Same as (a) and (d), for flag F=1 stars only. (c and f) Same as (a) and (d) for flag F=0 only. The F=0 LOSs show no dependence, and lower the correlation based on all data. F=1 targets show a clearer positive correlation.