Acamera lucida is anoptical device used as a drawing aid byartists andmicroscopists. By looking through theprism in its standard, a user sees anoptical superimposition of the subject positioned in front of the device over the surface below. This allows the artist to duplicate key points of the scene on the drawing surface, thus aiding in the accurate rendering of perspective.
Thecamera lucida was patented in 1806 by the English chemistWilliam Hyde Wollaston.[1][2][3]
The basic optics were described 200 years earlier by the German astronomerJohannes Kepler in hisDioptrice (1611), but there is no evidence he constructed a workingcamera lucida.[4] There is also evidence to suggest that the Elizabethan spy Arthur Gregory's 1596 "perspective box" operated on at least highly similar principles to the latercamera lucida, but the secretive nature of his work and fear of rivals copying his methods led to his invention becoming lost.[5] By the 19th century, Kepler's description had similarly fallen into oblivion, so Wollaston's claim to have invented the device was never challenged. The term "camera lucida" (Latin 'well-lit room' as opposed tocamera obscura 'dark room') is Wollaston's.[6]
While on honeymoon in Italy in 1833, the photographic pioneerWilliam Fox Talbot used acamera lucida as a sketching aid. He later wrote that it was a disappointment with his resulting efforts which encouraged him to seek a means to "cause these natural images to imprint themselves durably".
In 2001, artistDavid Hockney's bookSecret Knowledge: Rediscovering the Lost Techniques of the Old Masters was met with controversy. His argument, known as theHockney-Falco thesis, is that the notable transition in style for greater precision and visual realism that occurred around the decade of the 1420s is attributable to the artists' discovery of the capability of optical projection devices, specifically an arrangement using aconcave mirror to projectreal images. Hockney was inspired after seeing drawings byIngres, which he came to suspect were made with the aid of a camera lucida.
Thecamera lucida is still available today through art-supply channels but is not well known or widely used. It has enjoyed a resurgence as of 2017 through a number of Kickstarter campaigns.[7]
The name "camera lucida" (Latin for 'light chamber') is intended to recall the much older drawing aid, thecamera obscura (Latin for 'dark chamber'). There is no optical similarity between the devices. Thecamera lucida is a lightweight, portable device that does not require special lighting conditions. No image is projected by thecamera lucida.[citation needed]
In the simplest form ofcamera lucida, the artist looks down at the drawing surface through a glass pane or half-silveredmirror tilted at 45 degrees. This superimposes a direct view of the drawing surface beneath, and areflected view of a scene horizontally in front of the artist. This design produces an inverted image which is right-left reversed when turned the right way up. Also, light is lost in the imperfect reflection.[citation needed]
Wollaston's design used a prism with four optical faces to produce two successive reflections (see illustration), thus producing an image that is not inverted or reversed. Angles ABC and ADC are 67.5° and BCD is 135°. Hence, the reflections occur throughtotal internal reflection, so very little light is lost. It is not possible to see straight through the prism, so it is necessary to look at the very edge to see the paper.[8]
The instrument often came with an assortment of weak negative lenses, to create avirtual image of the scene at several distances. If the right lens is inserted, so that the chosen distance roughly equals the distance of the drawing surface, both images can be viewed in goodfocus simultaneously.[citation needed]
If white paper is used with thecamera lucida, the superimposition of the paper with the scene tends to wash out the scene, making it difficult to view. When working with acamera lucida, it is often beneficial to use toned or grey paper. Some historical designs included shaded filters to help balance lighting.[citation needed]
As recently as the 1980s, thecamera lucida was still a standard tool ofmicroscopists.[4] It is still a key tool in the field of palaeontology. Until very recently,photomicrographs were expensive to reproduce. Furthermore, in many cases, a clear illustration of the structure that the microscopist wished to document was much easier to produce by drawing than by micrography. Thus, most routine histological and microanatomical illustrations in textbooks and research papers werecamera lucida drawings rather than photomicrographs. Thecamera lucida is still used as the most common method among neurobiologists for drawing brain structures, although it is recognised to have limitations. "For decades in cellular neuroscience, camera lucida hand drawings have constituted essential illustrations. (...) The limitations of camera lucida can be avoided by the procedure of digital reconstruction".[9] Of particular concern is distortion, and new digital methods are being introduced which can limit or remove this, "computerized techniques result in far fewer errors in data transcription and analysis than the camera lucida procedure".[10] It is also regularly used inbiological taxonomy.
{{cite book}}:|work= ignored (help)Wollaston, William H. 'An Instrument Whereby Any Person May Draw in Perspective, or May Copy of Reduce Any Print or Drawing.' British Patent no. 2993
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