1. Contrast Methods, e.g. self-built

Low and medium cost microscopes as well as older ones don't provide support for contrast enhancement such as dark field (costs: 100 Euro and above), phase contrast (250 Euro and above) or interference contrast.

Without contrast enhancement however, uncoloured objects-so-called phase objects - such as onion skin, the mouth's mucous membrane or zooplancton, can't be observed with great success. As a remedy, I have invented the following methods (1.1....) or greatly simplified on a do-it-yourself base.
tentacles of a small marine crayfish near Helgoland (Germany) magnified 250 times

This way or that way? The tentacles of a small marine crayfish near Helgoland (Germany) magnified 250 times (objective 25 times), above using diffraction contrast, below in normal bright field with strong diaphragming.

Only with strong diaphragming recognizable structures can be seen when using bright field illumination, however a disturbing diffractive blurring of the image occurs.

Coloration that sometimes makes sense for plant specimens is not advisable e.g. for living zooplancton etc.

The equipment of microscopes with dark field, phase contrast or differential interference contrast is too expensive. In nearly every microscope, the following contrast methods can be installed with some skill, and they have an effect similar to dark field or difference interference contrast.