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Rheinberg

The Rheinberg illumination, discovered in 1896 in London by Julius Rheinberg, is a technique that allows to give a different color to background and subject, and in some cases even to portions of the subject. The result is original, engaging the aesthetic point of view and with details more discernible inside the subject. This technique is closely related to the dark-field illumination method. In this case, however, the stop is changed so that the central black is replaced with a colorful stop, usually of plastic wrap. The color of the central area of the filter represents the background color microscopic image. The peripheral area of the filter will have a different color, possibly quite in contrast with that of the central area. The samples will take the color of the peripheral zone. These filters can be easily made using a color printer and glossy transparent sheets.
To obtain good results with this technique, it's need to observe some basic rules:

1. optimum height of the condenser
2. complete opening, or most, of the diaphragm condenser
3. appropriate light intensity.


In addition, to be able to faithfully record the image, you will have to adjust efficiently the parameters of brightness, contrast and color balance.

The subjects most suitable to this type of observation are diatoms, foramnifera, radiolarians, protists, algae and other aquatic life. Even small insects or parts of them are interesting to see, at low magnification, for the particularity to stain the various details of the subject in different ways.