Left-hand panel: photometric redshift histogram for SWIRE-EN1 sources with at least five photometric bands, and S(3.6) > 5 μJy. Top panel: all sources; lower panels: separate breakdown of contributions of ellipticals, spirals (Sab + Sbc + Scd) + starbursts (Sdm + Sb), and quasars. The histogram for quasars has been multiplied by 20. Right-hand panel: photometric redshift histogram for all SWIRE sources with three-band optical IDs, and S(324) > 200 μJy. Top panel: all sources; lower panels: separate breakdown of contributions of ellipticals, Sab, Sbc, Scd, starbursts (Sdm + Sb), and quasars. The histogram for quasars has been multiplied by 10.