Editing Halftone (section)

==Halftone photographic screening==
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. The photographic plate could then be developed using photo-etching techniques to create a printing plate.

Other techniques used a "screen" consisting of parallel bars (a [[Ronchi ruling]]), which was then combined with a second exposure with the same screen oriented at another angle. Another method was to expose through a screen-plate with crossing lines etched into the surface. Later, either photographic contact screens were used, or sometimes no screen at all, exposing directly on a lithographic (extremely high [[Contrast (vision)|contrast]]) film with a pre-exposed halftone pattern.