Contrast values from the main study plotted against grain sizes. Cases where s < s_BO,eff are shown as cross (×) marks, which overlap with other data points up to 1 μm. The dashed lines indicate the size-combined contrast values of optical depth $⟨C_{\tau }⟩$; see Sect. 3.2.2) for each spectral type. The colors and symbols follow those used in Fig. 4. However, only cases with M_p = 1 M_⊕ and a_p = HZ_mid are considered here, resulting in eight points for each spectral type. The contrast for 300 μm dust around the K-type star is only slightly lower than that for M-type stars, nearly overlapping and therefore hidden from view.