Completeness of the RCS2 component of the CFBDS survey as a function of z′ magnitude and i′ − z′ colour. The colour bar ranges from 0% (blue, all objects went out of the selection limits) to 100% (red, all objects detected). The volume-weighted average completeness over our selection criterion (black rectangle, i′ − z′ > 2.0 and z′ < 22.5) is 73%. This plot also highlights the contamination of our sample by objects whose actual colours and magnitudes lay outside our selection box but are scattered inside by photometric errors.