Left-hand panel: photometric versus spectroscopic redshift for SWIRE-VVDS sources, using four optical bands only (ugri) and requiring r < 23.5. Right-hand panel: photometric versus spectroscopic redshift for SWIRE-VVDS sources, using four optical bands (ugri) + 3.6, 4.5 μm, and requiring r < 23.5, S(3.6) > 7.5 μJy.