The sellers of loupes will claim that magnification is not as important
as actual image definition and resolution. In fact, already a high quality 3x loupe
can provide stunningly crisp images and can turn out as an extremely useful tool
when e.g. soldering small electronic parts or when looking at some of the bigger
bugs and plants in nature.
For many tasks in everyday life a good 3x loupe is the optimum dedicated viewing device, a 10x
loupe often might be stupid over-kill and silly money in those applications - in so far
the vendors are perfectly right.
But the tardigrades, as we all know, are somewhat special. A good optical quality alone
might be not sufficient in this case. Why? You see, the bare eye is able to resolve two
points when they are at least 0.12 mm apart. This means that for the eye a 0.2 mm tardigrade will
appear as a two pixel object at best. With a 10fold loupe this multiplies up
to 20 pixels which is still a very poor image size, like the Windows® hour glass icon.
There is an inevitable conclusion:
A 10fold magnification as a rule will be not enough for our tardigrade studies!
There exist (fewer) loupes with higher magnification numbers than 10x.
We have already pointed out in the last issue that optical disadvantages
go hand in hand with the higher magnifications:
small usable lens diameters, small field of view,
need for additional (artificial) light, small focus depth, short working distance
and the need for an extremely clean parallel orientation of the lens and the object area
By the way, do you know why some older loupes are equipped
with mysterious holes in the mounts (as shown in the last issue)? Here is the answer:
they will help to achieve a perfect parallel orientation of lens area and investigation area.
Have a look at this: