/oʊˈpeɪk prəˈdʒɛktər/

Opaque projector

noun · drawing tool

What it is

Most projectors need a transparent source: a slide, a film cell, or a screen that light shines through. An opaque projector works the other way. A lamp inside the housing floods a solid original — a photo laid face-up, a page from a book, a small sketch — and a system of mirrors and a lens gathers the light bouncing off it, then throws that image, enlarged, onto a wall or canvas. Because the source is reflective rather than transmissive, the machine can project anything flat without first making a transparency of it.

For an artist the appeal is scale. A palm-sized reference can be enlarged to fill a two-metre mural, and the projected outline is traced onto the surface in the darkened room. That is the shared job of the projector method. Unlike the light box, which only copies at the reference's own size through thin paper, the opaque projector enlarges; unlike AR tracing, it casts real light and so needs a dim room and a fixed setup.

Etymology

The name pairs "opaque" — from the Latin opacus, "shaded" or "not transparent" — with "projector," describing exactly what the device does that a slide projector cannot: it projects an opaque source. The optical unit at its heart is the episcope; a machine able to project both opaque and transparent originals is called an epidiascope. Consumer models such as the mid-20th-century "Opaque Projector" made the tool a fixture of classrooms and studios before digital projectors and, later, phone-based methods largely replaced it.

Examples in use

A muralist tapes a printed colour study near the projector, dims the wall lights, and traces the enlarged outline in chalk before painting. A sign painter projects hand-lettered artwork onto a board to scale the letters cleanly. A scenic painter blocks in a backdrop from a small maquette. The method demands a dark room, a level machine, and a fixed throw distance — constraints the AR tracing app removes by registering the reference over the real surface on a phone screen in normal light, while the free web tool handles the 82 composition overlays for planning the design first.