Transmission spectrum of TrES-3 b. Shown is the GTC/OSIRS spectrum (crosses). The broadband photometry is indicated with squares. The response function for each photometric band is shown at the bottom. Horizontal error-bars indicate the FWHM of the band. The narrow band observations by Colón et al. (2010) are indicated with a triangle. The results of the previous study by P16, their Fig. 9, are shown for comparison with an arbitrary offset of -75 Å for clarity. All vertical error-bars indicate the 1 σ uncertainty.