Changes in Δσ_⋆ with the E(B − V) distribution in the ring in NGC 1097. We plot the results for three different target S/N for the GIST pipeline analysis (the blue series): 100 (left panel), 250 (central panel), and 350 (right panel). We can observe how the highest values of the colour excess disappear when we increase the S/N. At the same time the highest values of Δσ_⋆ start to decrease. At S/N = 350 we cannot clearly discern the trend we observe for S/N = 100 and the distribution for the ring of NGC 1097 is similar to that for that of NGC 5248.