The circle sizes is proportional to W_λ(5797)/W_λ(5780). Black and white circles indicate ζ and σ sightlines, respectively. Seven of the eight stars (one is outside the map) generating 90% of the local ISRF (Sujatha et al. 2005) are indicated by bold circles with italic numbers. The “high-density” (ρ Oph cloud) and “low-density” regions selected for comparison are delineated by the black and white square, respectively. Intermediate classified lines-of-sight are labeled with an “i”. Note that for HD 149438 no DIBs were detected, but it is included here for its large contribution to the local ISRF. Targets labeled with “*” have relative errors on the ratio between 30 and 60%, while errors larger than 60% are omitted. All other targets have errors smaller than 30% (see also Table 2).