Amici’s design uses a clear glass plane, shown here in pink cross-section, and (to its left) an adjacent front-surface mirror. Here is one of Amici’s proposals for a “See-Through” camera lucida, in 1818. This diagram is adapted from Amici’s paper (note: we have colored Amici’s image and added the eyes above it): In Sopra le camera lucide (1818), he concedes the basic flaw in his design-and in all “See-Through” camera lucidas to follow. He thought the proximity of the eye to the prism’s edge was too close for comfort, and so he developed a variety of models with combination glass and mirror elements. Giovanni Battista Amici, an Italian 19th century astronomer and mathematics professor, was among the first to propose “See-Through” alternatives to Wollaston’s foundational prism design. This can be mitigated by the use of pellicle beam splitters (a kind of reflective film) and first-surface mirrors (such as polished metal), but these are considerably more expensive and highly susceptible to damage (such as from dust, fingerprints, oxidation, and scratches). The eye interprets these as “out of focus”-and therefore difficult to trace. The user’s view may therefore be a composite of up to four reflections, each showing the scene from a slightly different angle and position. When the lighting is well-balanced between inside and out, you’ll see two images superimposed like this: If you’ve ever seen a double-image in a glass storefront, that’s the principle. When you look through the glass, you see the reflection of your subject plus your paper at the same time, superimposed. The “See-Through” camera lucida makes use of an angled piece of transparent or semi-transparent glass. (Of course, there are many other technologies for “tracing what you see”, such as opaque projectors, the camera obscura, and even tracing paper-but these use entirely different optical principles.) The “See-Through” design was developed more recently, and is used in commercial devices like the Lucid-Art we’ll discuss it first. As a shorthand, we’ll call these the “See-Through” design, which uses planes of glass and mirrors, and the “Split-Pupil” design, which uses a solid glass prism. Historically, there have been two basic design paradigms for the camera lucida. How does a camera lucida overlay two images?Ĭamera lucidas allow you to “trace what you see” by superimposing two views: that of your subject (such as a landscape, portrait, still life, etc.), and that of your paper. Along the way, you’ll see how we came to make some of our decisions about the optical design of the NeoLucida. The camera lucida, patented by William Hyde Wollaston in 1807, is essentially a “prism on a stick.” The stick part is easy to understand, but exactly how does the prism work? What sorcery lives in that little block of glass? In this “Interlude” update, our fourth, we present a detailed “how it works” about camera lucida optics. It's a little bit more than just a "prism on a stick."
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