The big water bear dark field image

Most readers seem to prefer dark field photomicrographs of the water bears. But some think that sophisticated equipment might be necessary, like the splendid "Microbe Hunter" microscope made by the Steindorff Company, Berlin, around 1950:

The "Microbe Hunter".
This particular instrument was built in 1954.
It has a triple condenser revolver with a dedicated dark field condenser (the right condenser under the table).

But there are cheaper ways to darkfield photographs. Even modest second-hand instruments can be easily adapted to dark field illumination. A simple black paper disc, with a diameter between 4 mm to 1 cm (one has to try) will provide dark field when being placed on the filter holder. The procedure should work for weak to medium magnifications up to about 20x objective magnification. By this the direct light cannot pass through to the object which then will be reached by indirect light only.The following illustrations show how it is done.

Left: vintage microscope (Zeiss, 1940s).
The red arrow marks the filter holder.

Right: Detail, filter holder under the condenser. Custom-made paper disc on the matte filter.

Left: view through the microscope during adjustment of position of the black paper disc. The paper disc appears as a blurred partially black background. The iris should be opened at the beginning of the adjustment. When the height of the condenser is changed optimum contrast can be found.

Right: fine positioning of the paper disc by means of a toothpick.

Left: Egg of water bear Macrobiotus hufelandi. Normal bright field illumination.

Right: Egg of water bear Macrobiotus hufelandi. Dark field illumination.

Do you want to see how all this works on water bears? Just click  here! 

In particular montage can be easily performed on dark field photomicrographs. The big image shown is in fact a montage of a single water bear in different stages of movement.

In the next issue we will see a fine "Fly-by" around a water bear tun in dry state. Stay tuned!