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