Mean F814W surface brightness (see text) versus I-band (F814W) total magnitude. Black dots: Cosmos (Scoville et al. 2007) HST ACS detected objects with a 68% photometric redshift error lower than 0.2 and a photometric redshift between 0.1 and 6. Only one object over 100 is shown for clarity. Red circles (Elliptical1 in the Cosmos templates), blue dots (Sa0 in the Cosmos templates), and green crosses (Sd0 in the Cosmos templates): the three detected diffuse light sources in CL J1449+0856 assuming different redshifts and different types for the three sources. This allowed us to translate H-band to I-band magnitudes. The vertical red line is the assumed Cosmos completeness total magnitude in terms of surface brightness (I = 23.75: see text). The inclined straight lines show the fits of the Cosmos detection limits (broken lines) computed for total magnitudes I ≤ 23.75 (red: 3σ, green: 2.5σ, blue: 2σ): see also text.