A magnetic brush developer apparatus comprises a plurality of developer housings (32, 34) each including a plurality of magnetic brush rolls (35 - 38) associated therewith. Conductive magnetic brush (CMB) developer is provided in each of the developer housings. The CMB developer is used to develop electronically-formed images. The developer conductivity is in the range of 10- 9 to 10- 13 (ohm-cm)- 1 . The toner concentration of the developer is in the order of 2.0 to 3.0% by weight; the charge level is less than 20 microcoulombs/gram, and the developer rolls are spaced from the charge-retentive surface a distance in the range of 1.0 to 3.0 mm.