 By the 1880s, Hoen was working on halftone methods that could be used in conjunction with either hand-worked or photolithographic stones.Prior to digitised images, special photographic techniques were developed to break grayscale images down into discrete points.The earliest of these was "screening" where a coarse-woven fabric screen was suspended before the camera plate to be exposed, breaking the incoming light into a pattern of dots via a combination of interruption and diffraction effects.