The photosensitization stencil process requires an independent matrix, usually produced on transparent film – a so-called photolith, if generated photomechanically; or a slide/film positive, if generated manually or digitally. Currently, the term photolith is still used, derived from what was the lithographic photomechanical and which expanded to other printing techniques. A photomechanical process means that the mechanical phase (printing) depends on a photographic phase, which implies a light-capturing process. Before the computer age, a photolith was effectively generated by photographing and developing an original on a sensitized surface (a complex compound of insulating layers, sensitized with silver chloride), in a darkroom. Much later, the process ended up giving way to a simple photosensitive film, which was already printed by an imagesetter – a sophisticated piece of equipment that emerged in the 1980s, connected directly to a computer and which prints by a process identical to laser printing (helium-neon laser, at very high resolution). Later, with the advent of common laser and inkjet printers, the process became as simple as a home print, without the need for sensitization or any spectral treatment of the film, using materials as accessible as tracing paper, engineering paper, matte polyester, transparent vinyl, or suitable acetate. However, imagesetters did not cease to exist; they evolved into various modern equipment solutions, depending on high-quality and precision printing areas, still requiring a high-performance sensitized film that constitutes the current photolith. However, and in some professional environments, the term tended to expand to common laser printers, perhaps by ideological association, since these still involve a process between a specific beam of light and an internal photosensitive drum. In professional printing circles, the term photolith is well distinguished, considering that a sensitized film applied to an imagesetter is incomparable to a common film, both in structural quality and in the high-precision printing process in terms of density, definition, and registration. Furthermore, the matrix engraving operated by an imagesetter continues to be done directly on the film, unlike the indirect process of the common laser printer. Given the increasingly frequent use of inkjet printing, even in professional equipment, the term photolith no longer makes any sense, so the term film positive became more appropriate.
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