Tardigrades, naturalists and the triplet distress (V)
Fig. 1: Echiniscus tun (tardigrade in the dry state),
visual impression when looking onto it with a good 20x handheld magnifier, in transmitted light.
Fig. 2: The same scenario as above showing the visual impression when concentrating on the center of the field of view.
When comparing this to the view through a typical compund microscope you might feel a little bit disappointed as far as the loupe is concerned. But, still, the magnifier is far better than the bare eye.
Fig. 3: Echiniscus tun, as seen
under the classical compund microscope (left), compared with the 20x hand magnifier (right).
The magnifier image was zoomed to the same scale.
The small markers on the scale are depicting 1/100 mm intervals (10 µm),
with the length of the tardigrade being approximately 140 µm (0.14 mm).
This is a truly tiny object for a magnifier and not too big for the microscope either.
Nevertheless, just for the sake of completeness we would like to
mention that there exist a few magnifiers ranging above the 10x, 20x or 28x range.
And no, these needn't be fraudulently labelled items. But please, be warned that there are many internet
auction items claiming high field of view diameters in combination with
exaggerated magnifications. A "40x" handheld magnifier with 30 mm lens diameter is double nonsense, of course:
In many cases the mag specifications are not correct. And extremely high mag loupes will always
come with extremely small lens diameters.
So-called "Algensucher" instruments (extreme single-lens magnifiers).
Two different systems, the right one is probably marking a world miniaturization record.
Small version of the "Algensucher" instrument, as shown in fig. 4. Early 1900s.
This one with ca. 50x magnification has to be considered as extremely rare.
It is measuring merely 2.7 cm in height, with a maximum diameter of 2 cm,
weighing 20 g (all brass and a tiny glass lens).
It is probably the smallest stand-alone microscope worldwide! The top part
bears a 1 mm lens and can be shifted above the base part for focusing.
When the top part is fully removed, the transparent "specimen table"
This table consists of a glass plate with a frosted ring in the center.
The instrument is working without a slide (!): a water droplet can simply
be placed in the area of the frosted center mark ring in order to be screened for algae.
Still rarer are extremely high-mag folding magnifiers. They are objects of glamour
for use by the extreme specialist in the field. Just have a look at the following
example of this bizarre species:
Fig. 6: Ultra rare, extremely strong, extremely tiny folding magnifier. We measured a magnification value of ca. 40 to 45. This is in perfect agreement with its engraving reading "6" (as a focal length of 6 mm is equivalent to a 42fold magnification). We think that those magnifiers were produced only in small numbers, for scientists, universities etc. The one shown was probably made in the early 20th century. The material appears to be nickel-plated brass. Its weight is 13 grams.
Fig. 7: Detail view of the head of the magnifier shown in fig. 6. Please note the conical lens housing which is helpful in order to let a sufficient amount of ambient light find its way to the subject. The lens is tiny and it takes some practice to cleanly focus onto the subject. The optical quality and excellent usability are due to the true Steinheil triplet system (fig. 7) but also to a clever shield against stray-light by means of a recessed lens in a black cavity. Remember that no coated optics existed at the time of production. Overall the resolution and image quality are a dream and there appears to be no modern equivalent to this type of instrument.
Fig. 8: Optics of the
ultra compact, ultra rare folding magnifier shown in fig. 6.
This is a true, miniaturized Steinheil triplet, made up to three cemented lenses!
The outer diameter is only 5 mm.
The magnifiers shown here are still ranging below the average collector's
mental radar and probably will remain so. Those among you who are not proud owners
of this type of instrument should console themselves by the fact that even the
most modest dissecting microscope (in the 50 US $ range) will perform much better in the field.
© Text, images and video clips by
Martin Mach (firstname.lastname@example.org).