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Magnifiers: a closer look (VI)
'Flattering' inscriptions

As already explained previously, a 10x magnifier with circular LED illumination will be the best suited instrument in order to spot tardigrades in dry moss cushions (many tardigrades in the dry state will reveal a distinct blue color under those conditions). Obviously, smaller magnifications will not be sufficient to detect those tiny tardigrade 'tuns', whereas higher magnifications will make you struggle with insufficient focus depth and terribly low working distance.

In any case you will find many internet offers with seemingly high magnification folding magnifiers. But in particular, most "30x" magnifiers are simply mislabeled or pure fraud.
A century ago, the palette of folding magnifiers was much more serious and honest. They could be expensive and some were even depicted on book covers:

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Fig. 1: William James Wintle's "Recreations with a pocket lens" (London, 1911) is showing a double-sided pocket magnifier on its cover. One side is bearing two biconvex lenses, each with an estimated magnification of ca. 5x (summing up to 10x). On this side there is also an in-between iris lever, intended to improve image quality. The other side is equipped with a tiny, single, stronger magnifying lens, possibly 20x. The small lens is the luxury part of the instrument, adding some glamour to the workhorse character of the weaker lenses, thus marking the connoisseurship of its proud owner ...

Within Wintle's book there is also a "Pond life" illustration showing two tardigrades. Nevertheless the author doesn't refer to tardigrades within the book's text - not surprisingly, as a hand magnifier might be able to detect the tardigrades but will not be sufficient for a more intense study in detail.

[ Ultra-Einschlaglupe ]

Fig. 2: The "Pond life" image in Wintle's book is illustrating an idealized water droplet microcosm, with everything included: Melicerta ringens, Stentor, Volvox, diatoms etc.

[ Ultra-Einschlaglupe ]

Fig. 3: This crop of fig. 2 is concentrating on the tardigrades crawling on some vegetable material (water milfoil).

The layman's wish for a high-magnification bargain magnifier nowadays is "served" by myriads of instruments with fraudulent inscriptions. But, as most customers will be better off with ordinary 10x magnifiers the fraudulent character can be regarded as a minor sin.

[ Ultra-Einschlaglupe, Optikfassung  ]

Fig. 4: "10x", "20x" and "30x" magnifiers arranged on a glass plate, ca. 3 cm above a millimeter paper. Obviously, the optical effect is the same for all three of them, thus indicating that at least two of the group are bearing faulty magnification numbers.

In addition, the term "TRIPLET" is suggesting the existence of a high quality cemented triplet system (made up of three lenses of two different glass types). But be warned that the term "TRIPLET" is just a brand name in this case, sadly mimicking the real thing: those three magnifiers shown do contain only a single, rather primitive cylinder lens.
Nevertheless the three cheapies still will be able to serve as basic 10x magnifiers, good enough to allow a casual look at some beetle's legs or printer ink spots.

Some of the "30x" labelled magnifiers might be far off from reality, others a bit more close to the truth. Just have a look at the two following examples:

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Fig. 5: A silver colored "30x17" magnifier and a gold colored "30x36" magnifier. Both are looking mechanically solid, with a nice finish.

The two magnifiers shown in fig. 5 are bearing faulty, or possibly slightly fraudulent inscriptions:

On the positive side it should be mentioned that the lenses of the silver color "30x17" magnifier are in fact coated. Inside we found a three lens optical system, made up of a cemented doublet plus a single lens, the latter separated by a spacer ring. A visual inspection is confirming the achromatic character and the clean resolution of a 10µm spacing (on a so-called object micrometer). Overall this is a high quality magnifier, even though the actual magnification appears to be closer to 20x than to the specified 30x.

The "30x36" magnifier appears to be more problematic as its magnification is not 30x as indicated but close to 10x. An internal inspection is revealing a classical system of two bi-convex lenses, This is still enough for an acceptable optical performance. As to be expected this magnifier is not able to resolve a 10 µm spacing (like the one as mentioned above). But this is not a consequence of optical quality but of lacking magnification power - 10x is simply to low for the task.

It goes without saying that the instruments shown above cannot come close to the "Winkler&Wagner" folding magnifier presented in previous issue of our magazine.

On the other hand we should not forget that some older magnifiers of British origin can be very competitive even though they might bear no inscription whatsowever and contain single lens optics:

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Fig. 6: Illustration of a Brewster type magnifier in a 19th century microscopy book (image source: Jabez Hogg, The Microscope , p. 26, London 1854).

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Fig. 7: The same instrument as in fig. 6. Actually it is quite usable and we think that its magnification is very respectable, amounting to an estimated true value of ca. 25x.

Though the design of the Brewster lens might appear to be inferior to the more recent triplet system a practical check is showing that it is definitely able to resolve fine detail. In fact it is clearly reveiling the 10 µm ruling as mentioned above. The single lens design comes at a price though, which is a relatively small field of view. But the slim design with its thin side walls is quite helpful in order to illuminate the object under investigation by means of natural daylight. Overall this is a very nice system, possibly a for Lords only understatement gadget!

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
The 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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