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Small take-along helpers: Loupes (III)

In the last   issue  we had discussed the tardigrade visual impressions provided by a good 10fold 'Steinheil' loupe. Though the optical quality of the loupe was excellent we came to the conclusion that the magnification was simply too low in order to deliver enough tardigrade detail.

This is why we are trying stronger loupes now, with up to 30fold magnification.
Our experimental set-up is as follows: we use a tiny light-box (designed for a single photographic slide), with cold LED light, on order not to do any heat harm to the tardigrades. The micro aquarium is simply placed upon the light-box:

[ Small light-box designed for photographic transparencies ]

Small light-box, with battery, as a source for smooth transmitted light. On top you see our usual micro aquarium with the 'miracle type' water column tardigrade cage.

The battery-holder of the light-box can serve as a base, e.g. in connection with a 20x 'Betamag' loupe:

[ Light-box, micro aquarium and Betamag loupe ]

Betamag loupe with 20fold magnification.

The Betamag loupe has a focusing thread. This is quite comfortable, at least when compared with other, 'naked'loupes but it might be a challenge for nervous people or those with thick fingers.
But after some exercise most people will reach a certain level of excellence and are awarded by a crystal clear image, satisfying even very choosy individuals. It is a pity that our photographic camera is not able to fully grasp the tremendous image clarity and definition:

[ View through the Betamag loupe ]

View into the micro-aquarium as provided by the 20fold Betamag loupe. There is no doubt that we get much more detail than with any 10fold loupe (cf. last issue). The four eggs within the Milnesium cuticula (position 11 o'clock) reveal already a little bit of inner structure.
The body length of the red Echiniscus tardigrades is about 0,3 mm. The female moving up vigorously was too quick for our camera shutter time - which is not a flaw of the loupe.

As often, when some progress is achieved, people don't celebrate the success but eagerly look out for an enhanced success. This is why we are switching to the 30x magnification webcam loupe as presented in the last issue.

[ Light-box, webcam objective as loupe ]

The glass objective of an technically outdated webcam serving as an excellent loupe. 30fold magnification. The field of view and image brightness appear slightly inferior to the Betamag loupe but this drawback is made up by the enhanced detail.

Focusing also in this case remains a challenge but it is worth while:

[ View through the WebCam loupe ]

View through the WebCam loupe. The field of view is rather limited but the tiny Echiniscus water-bears come out perfectly with crisp detail. 'Nose' tips and claws can be felt (or seen with a little bit of fantasy).

[ Blick durch die Webcam-Lupe ]

Second view through the webcam loupe. The black eyes and band texture of the central Milnesium tardigrade become visible. The grey eggs of Macrobiotus hufelandi (position 4 o'clock) reveal their egg protrusions. The orange Echiniscus tardigrade egg (center, right) still cannot be studied in detail - in spite of the impressive 30x magnification number. It has a very modest diameter, about 40 µm.

Alltogether the results are not too bad for an instrument weighing just 8 grams. When using it on top of the Mount Everest you might even consider to skip the light-box and use the diffuse snow-reflected light instead ;-).

After our first experiments with simple magnifier systems (one step magnifiers) we can easily image how Antoni van Leeuwenhoek (1632 - 1732) eagerly improved his one-lens systems, creating smaller and smaller lenses with increasing curvature and increasing magnification.
In the 19th century many scientists tended to doubt that he actually had properly seen those bacteria and red blood cells as decribed by him. But 20th century authors like Brian J. Ford and Klaus Mayer closely followed Leeuwenhoeks assumed procedures and actually proved that he had been able to see all the reported details just with a single lens loupe. Klaus Mayer points out in his book how everbody can smelt one's own globular 100x lenses just by means of smelting a glass fiber end until it transforms into a spheric lens.

[ Leeuvenhoek-Mikroskop ]

Leeuwenhoek microscope (ca. 1690). Left: user side with small viewing window. The tiny loupe is hidden behind the 'swollen' opening. The eye has to be kept very close to the lens.
Right: view of the object side with focusing device and object fixing needle. Picture from William B. Carpenter, The Microscope and its Revelations (1891).

'One-step' dissecting microscopes basically following the Leeuwenhoek construction principle were built well until into the 20th century and belonged to the typical life scientist's professional equipment - in spite of the modest ergonomics and the very short working distance.

[ dissecting microscope, middle of 19th century ]

Dissecting microscope, middle of 19th century. Please note the extremely small focusing distance between object level h and lens q in lens holder p. Picture from Jabez Hogg, The Microscope (1854).

In the next issue we will point out that cheap dissecting microscopes ('stereo microscopes') are able to perfectly compete even with the most expensive loupes.

Sources of the historic illustrations

Leeuwenhoek microscope from: William B. Carpenter, The Microscope and its Revelations. p. 134. London 1891.

Dissecting microscope from: Jabez Hogg, The Microscope. p. 27. London 1854.

Written sources and recommended literature for further study

John Field: Leitz Simple Magnifiers.
The Journal of the Microscope Historical Society, 12 (2004) 52 - 60. ISSN 1545-2077.

Brian J. Ford: Frühe Mikroskopie. Spektrum der Wissenschaft, issue 6 (1998) p. 68 - 71.

Brian J. Ford: Single Lens. The Story of the Simple Microscope. 182 pages. New York 1985.
ISBN 0-06-015366-0.

Klaus Mayer: Geheimnisse des Antoni van Leeuwenhoek. 647 pages plus 8 tables.
Lengerich 1998. ISBN 3-931660-89-3.

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed.

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