Slit-reconstructed images of the four raster scans centered at the He I line core of the red component (upper row) and the Ca II line core (lower row). From left to right: pre-flare (panels a and e), flare (panels b and f), and post-flare maps (panels c, d, g, and h). The white box shows the common FOV among all raster scans. The letters a–d in panel f mark the position of the pixels shown in Fig. 4. The light blue and pink crosses in panel f mark the positions of the response functions shown in Fig. 2. The red contours mark the borders of the flare ribbons in panels b and f, using an intensity threshold of I/I_c = 0.87 in the line core.