Systematic & Applied Acarology 21(9): 1278–1280 (2016) http://doi.org/10.11158/saa.21.9.10
ISSN 1362-1971 (print) ISSN 2056-6069 (online)
Correspondence
Video projector: a digital replacement for camera Lucida for drawing mites and other microscopic objects PHILIPP E. CHETVERIKOV 1, 2* 1
Department of Invertebrate Zoology, Saint-Petersburg State University, Universitetskaya nab., 7/9, 199034, St. Petersburg, Russia 2 Zoological Institute, Russian Academy of Sciences, Universitetskaya Embankment 1, 199034 St. Petersburg, Russia *Corresponding author. E-mail:
[email protected]
Key words: drawing invertebrates, Eriophyoidea, microarthropods, biological drawings
Describing various microscopic animals, such as mites or other microarthropods, requires slidemounting and making detailed drawings, which is both time-consuming and technically challenging. Only in rare circumstances can scientists draw a microscopic object correctly by observing them under a microscope without any special tools. Traditionally, acarologists draw mites on paper by pencil or ink using a special drawing tube, camera lucida, connected to the microscope (de Lillo et al. 2010). A more modern approach involves making digital illustrations using a stylus, interactive pen displays or pen tablets, which are all connected to a computer. In this case the microscope should be equipped with a video camera, allowing observation of the object on the screen of the monitor. The image is then traced using a stylus and pen tablet. Recently in their ingenious paper, Sidorchuk & Vorontsov (2014) described how to use VLC media player (free software) and an overlay mode for drawing mites by stylus without buying special expensive licensed software. Unfortunately, I was not able to adopt their methodology because the operational system used in the computer network of Zoological institute of RAS was incompatible with the version of VLC media player recommended by Sidorchuk & Vorontsov (2014). However this constraint coerced me to invent another very easy way for drawing mites using a video projector. A NEC NP VE281XG projector was installed on a shelf above the monitor near the microscope (Fig. 1). An aperture for light was carved into the shelf. The distance between the surface of the table and projector was chosen so that the projected image fits A4 paper format (53 cm above the table in this particular case). The projector was connected to a computer, and in the Display settings the option “Duplicate these displays” and the appropriate resolution were chosen. As a result, a very sharp and distinct live image captured by video camera was projected. This methodology works really well. For example, recently the early-derivative eriophyoid mite species Pentasetacus plicatus Chetverikov & Petanović 2016 and two sierraphytoptine species from relict eudicots (Chetverikov & Craemer 2016) were figured using a video projector. The described methodology has several distinct advantages: 1) in comparison to camera lucida, the projected image is much brighter due to the powerful lamp of the projector—moreover, even if the slide-mounted object is pale and weakly contrasted under the microscope, the contrast can be digitally adjusted, and as a result the object can be correctly drawn in detail; 2) the video projector allows not only changing brightness and contrast, but also zooming, which is especially useful for drawing morphologically complex or extremely small structures—additionally this may be useful for older scientists and persons with limited vision; 3) there is greater control over the drawing process because the same object can be seen thrice—under the microscope, on the screen, and as a 1278 © Systematic & Applied Acarology Society
projection on paper; 4) video projectors are readily available to buy compared to a Camera lucida; 5) finally, drawing with a video projector might be easier for novice researchers, who have no experience using a camera lucida.
FIGURE 1. Photograph showing how to use a video projector for drawing microscopic objects. Notations: a— microscope camera, b—cable of the camera, c—projector, d—projector power cable, e—VGA cable for connecting projector with computer, f—a self-made wooden shelf for projector, g—aperture for light, h—a sheet of paper. Remark: the projected image is not seen because it is overexposed due to much more bright light intensity of the projector in comparison to surrounding light; the system unit of the PC is out of the photograph frame because it is situated under the table. 2016
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The characteristics of the video projector are especially important to the successful utilization of this tool for drawing microscopic objects. Currently, most video projectors have a halogen lamp as a source of light. However a lot of LED models are available. In general, most contemporary LED projectors produce less bright light, and therefore halogen lamp projectors are preferable even though they are noisier because of the sound produced by the cooler. According to my experience, any projector with minimal focus distance at about 0.7‒1.0 m, minimal image diagonal of about 50‒90 cm, hand zoom and halogen lamp at about 2000 lumen can be used. The only potential problems associated with using such a projector for drawing is the need for extra space at the working place to install the projector, and the noise of the cooler. However these drawbacks are not significant in comparison to the general usability. Considering the main contemporary trend to manufacture ever smaller optical and electronic devices, it is possible that in the future, companies manufacturing video projectors or other optical tools will develop a compact specialized projector-based system for drawing microscopic objects compatible with a computer and microscope. It is quite expected that such a system will be in demand in the scientific and pedagogical community.
Acknowledgements I am grateful to Dr. S. Bolton (Ohio State University, USA) for linguistic corrections. This study was supported by the Russian Science Foundation (RSCF grant # 14-14-00621).
References Chetverikov, P.E. & Craemer, C. (2016) Sierraphytoptines (Eriophyoidea: Phytoptidae) from relict eudicots: reassignment of Sierraphytoptus taiwanensus to a new genus Solenoplatilobus and refinement of generic diagnosis of Austracus. Systematic and Applied Acarology, 21(6), 745‒758. http://dx.doi.org/10.11158/saa.21.6.3 Chetverikov, P.E. & Petanović, R.U. (2016) Description of a new early-derivative mite, Pentasetacus plicatus n. sp. (Acariformes, Eriophyoidea), and remarks on systematic position of pentasetacines. Zootaxa, 4144(2), 211–226. http://dx.doi.org/10.11646/zootaxa.4144.2.4 De Lillo, E., Craemer, C., Amrine, J.W. Jr. & Nuzzaci, G. (2010) Recommended procedures and techniques for morphological studies of Eriophyoidea (Acari: Prostigmata). Experimental and Applied Acarology, 51(1‒3), 283‒307. http://dx.doi.org/10.1007/s10493-009-9311-x Sidorchuk, E.A. & Vorontsov, D.D. (2014) Сomputer-aided drawing system-substitute for camera lucida. Acarologia, 54(2), 229‒239. http://dx.doi.org/10.1051/acarologia/20142130 Submitted: 8 Jun. 2016; accepted by Zhi-Qiang Zhang: 29 Jul. 2016; published: 22 Aug. 2016
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