Planck TT+lowE penalized likelihood primordial power spectrum reconstruction. Top four panels: deviation f(k) for four different roughness penalties. The red curves indicate the best-fit deviation, while the vertical extents of the dark and light green error bars indicate the ±1σ and ±2σ errors, respectively. The width of the error bars indicates the minimum reconstructible width (the minimum width for a Gaussian feature such that the mean square deviation of the reconstruction is less than 10%). The grey regions display where the minimum reconstructible width is undefined, meaning that the reconstruction in these regions is untrustworthy. The hatched region in the λ = 10⁶ plot indicates where the fixing penalty has been applied. Lower three panels: ±1σ error bars for the three non-primordial-specctrum cosmological parameters included in the reconstruction. The respective best-fit fiducial model values are indicated by the dashed lines.