ΣAf vs. ρ for NAC orange images of 67P/Churyumov-Gerasimenko obtained on April 20: black line (55 km/pix), April 24: red line (51.2 km/pix), April 27: green line (47.2 km/pix), April 30: blue line (43.8 km/pix), May 4: yellow line (38.9 km/pix), May 11: magenta line (30 km/pix), and May 18: cyan line (21.7 km/pix). For each observation, the pixel scale (in km per pixel at the comet distance) is indicated. The x-axis is in km and for each date, the spacecraft-comet distance is taken into account to convert pixel to km, whereas the y-axis is in arbitrary units.