Left panel: optical image of 3C 433 environment from GTC is shown in the background. Black contours show the radio continuum at 1.12 GHz as observed with the VLA. Contours start from 4σ (13 mJy beam⁻¹) and increase by a factor of 2. Our VLA radio image has a beam of 5.39″ × 4.72″, shown in the bottom right corner. Blue contours show the 3.6 cm map by Black et al. (1992). Contour levels start from 30 μJy beam⁻¹ (3σ) and increase by a factor of two. The region in the white box is blown up in the two images on the right panel. The radio core of 3C 433 as identified by van Breugel et al. (1983) is marked with a black cross. Right panel (bottom): blow-up of the image in the left panel with the H I column density (N_HI) contours shown in white. The N_HI contours start from 0.7 × 10¹⁸(T_spin/f) cm⁻² and increase in steps of 0.3 × 10¹⁸(T_spin/f) cm⁻². The image clearly shows that the H I absorber overlaps with an optical galaxy. Right panel (top): Hα contours (from GTC) overlaid on the optical image. The Hα contours levels are: (2.7, 3.2, 3.7, 4.3, 4.9, 5.4, 6 and 6.4) × 10⁻¹⁸ erg s⁻¹ cm⁻². The 3.6 cm radio contours (same as that in the left panel) are shown in blue.