Areas used for the flux calculation on the example of the [O III] lines in the continuum–subtracted spectrum. The ellipses represent the region used for the elliptical aperture photometry of the outer [O III]b line. The two red rectangles mark the areas of comparison between the outer [O III]a,b lines. The black rectangles indicate the region of overlap of the [O III]a line with the outer [O III]b material and the corresponding region for [O III]b. For details see the text.