Denoising and feature extraction for an SDSS ELG. The noisy spectrum (red) has been shifted up, and the error-curve (green) shifted down, for clarity. The vertical dashed lines (blue) indicate the locations of detected features that correspond to true emission features. The FDR denoising and feature extraction clearly pinpoints all of the major features without any difficulty. The three largest lines are, from left to right, the [O II] doublet, [O III] and H_α.