Optical (I, V–I) and hybrid (I, I–K) CMDs of Terzan 5 obtained through the combined HST and MAD observations, corresponding to the FOV delimited by the black box in Figure 1. No quality cuts and differential reddening corrections are applied to these diagrams. It is worth noticing the distortion of the evolutionary sequences along the direction of the reddening vectors, indicated by the black arrows in the upper-left part of the panels. The red line corresponds to a 12 Gyr old isochrone (Bressan et al. 2012; Marigo et al. 2017) with [M/H] = −0.2 dex, E(B − V) = 2.38, and μ₀ = 13.87 (reference parameters from the database of Valenti et al. 2007), reddenned by adopting R_V = 3.1. The dashed black lines show the same isochrone shifted by assuming R_V = 2.1, 2.6, 3.6, 4.1 (from left to right). We varied E(B − V) and μ₀ to fit the optical (I, V–I) CMD. However, despite the remarkable broadening of the evolutionary sequences, these alternative R_V values are clearly unable to match the hybrid CMD.