Transmission spectrum of WASP-33 b. Green circles and red diamonds correspond to the planet-to-star radius ratio obtained from OR1 and OR2, respectively. Gray light squares are derived fitting different detrending components to the data. Pink filled circles are from von Essen et al. (2014), and open black circles are considering larger integration bins. In all cases, error bars are at 1-σ level and horizontal lines indicate the size of the wavelength bin.