Abstract: Toning apparatus for toning an electrostatic latent image, having image and background portions at different potentials on an imaging surface. The apparatus comprises an endless toning surface coated with a layer of concentrated toner and engaging the imaging surface at a toning region. The apparatus additionally comprises a source: of voltage connected to the toning surface and electrifying the toning surface to a voltage operative to selectively transfer at feast a portion of the layer to image: portions on the imaging surface. A developed mass per unit area (DMA) controller having an input indicative of the DMA on the imaging surface is operative to adjust the DMA on the toning surface in response to the input.