Galaxy luminosity properties. Top left: Cumulative light distribution (blue line) for the Perseus cluster catalogue of 1220 galaxies, which reaches down to M(I_E) = −10. The absolute magnitude of the galaxy at the centre of each image cutout is indicated in the I_E band. While the 1083 dwarf galaxies dominate by number, 90% of the light in Perseus comes from the 83 galaxies brighter than M(I_E) = −19.5 (the remaining 48 galaxies plus all dwarf galaxies account for just 10% of the light in Perseus). Image thumbnails: The top left diagram is illustrated with seven examples of relative brightness and physical size, all presented at the same pixel scale. The range spans from the giant elliptical NGC 1275 (bottom left), which alone contributes 10% of the light in Perseus, to a dwarf 12 magnitudes fainter (bottom right). The colour for each magnitude bin matches the colour used to represent galaxies on the map of Fig. 24. All dwarf galaxies are fainter than M(I_E) = −18, while all other galaxies are brighter than M(I_E) = −16.