Overview

	Overview: Contrasting methods

	Carl Zeiss light microscopes offer a number of contrasting methods:		Overview Deutsche Version

	Brightfield Darkfield Phase contrast VAREL contrast Differential interference contrast (DIC) Polarization contrast Fluorescence

Brightfield

Classical microscopy method used especially in medicine and biology, e.g. for stained histological specimens such as tissue sections and smears.


Ground section of bone	Cystadenolymphoma, immunohistochemical staining of proliferating cells	Human blood

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Darkfield

This contrasting method can visualize fine structural features at, and even below, the limit resolution of a light microscope. Highly suitable for metallographic and crystallographic examinations with reflected light. Required: Special condenser, sometimes immersion oil


Ground section of bone	Hyoid bone of a mouse	Neurons

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Phase contrast

The phase contrasting method is excellently suitable for visualizing very fine structural features in tissues and single cells contained in very thin (< 5 µm), non-stained specimens that are otherwise very poor in contrast. Required: Special objectives and special condensers.


Ground section of bone	Thin phase specimens	Neurons

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VAREL contrast

VAREL is a contrasting method in which specimen structures show up in relief. As the method is insensitive to polarization effects (DIC!), it is specially suitable for specimens held in plastic vessels. Required: Special objectives, special condenser.


Myocardial cell of a rat, primary culture	Thin phase specimens in plastic vessels	Neurons

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DIC

The Nomarski differential interference contrast (DIC) method shows phase differences in the specimen in a relief-like fashion. The method is excellently suited for thick, non-stained specimens (> 5 µm). Required: Special, relatively expensive accessories in the illumination and imaging ray paths (prisms, polarizers).


Tongue. Fluorescence (DAPI) with DIC	Embryo of C. elegans. Prof. Schnabel, Technical University of Brunswick	Neurons

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Polarization contrast

Polarization contrast permits the identification of birefringent structures (crystals) in biological specimens. Main applications, however, are metallographic and crystallographic examinations with reflected and transmitted light. Required: Polarizer, analyzer, compensators.

$Bruchstelle Messingprobe - Brass specimen with a fracture$	$Bruchstelle Messingprobe - Brass specimen with a fracture$
Brass specimen with a fracture. Polarized light without compensator	Brass specimen with a fracture. Polarized light with compensator	Sulfide ore

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Fluorescence

The fluorescence method uses fluorochromes and special labeling techniques to visualize minute tissue and cell structures. The type of imaging (self-luminous objects) combines the highest possible detection sensitivity with the highest detection specificity (biochemical markers). Required: Reflected-light illuminator, filters, dichroic beam splitters, excitation light source.


Duodenum of a rat. J. Zbären, Inselspital Bern	Endothelium cells. Triple fluorescence: Nucleus (DAPI), F-actin (BODIPY-FL), mitochondria (Mitotracker Red)	Embryonic cells of a rat. Triple fluorescence. R. Learish, Promega Corporation, Madison, WI

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