Delay-corrected spectral flux ratio of SDSS J1001+5027. The delay-corrected r-band flux ratio (filled circles), and the single-epoch spectral flux ratio from Gemini North/GMOS (black line) and Keck/LRIS (deep purple line) are also shown. The three horizontal strips correspond to the C IV (purple), C III] (blue), and K-band (grey) flux ratios (see the end of Section 4.1), and are used to highlight the macrolens flux ratio.