Transmission spectrum of WD 1856+534 b. The radius of the WD is fixed to the estimated average value (0.0123 R_⊙), and the impact parameter is held fixed at a given value (8.5) as both parameters are independent of the wavelength. The larger filled circles mark the radius of the secondary in the Sloan g (cyan), Sloan i (green), and EMIR J (red) filters, while dark blue dots mark the radii determined at each spectral bin defined in Fig. 3. The solid blue lines in the background are random samples of the posterior of the linear fits to measure the atmospheric scale height. We note the logarithmic scale in the x-axis. The verticalscale on the right side gives the difference in kilometres from the mean radius of the secondary.