Comparison of the R_z − R_i parameter and of the spectral slope for the sub-sample of 14 129 asteroids observed both by Gaia and SDSS. We note that the slope distribution (panel A) of Gaia has a wing that extends to redder slopes than the SDSS. Panel B shows that the distributions of R_z − R_i for Gaia and SDSS are clearly shifted, with Gaia seeing a less deep Band I compared to the SDSS. Gaia and SDSS R_z − R_i parameter histograms can be superimposed when a constant value of 0.07 is subtracted from Gaia R_z − R_i-values.