Beyond Extreme Close-Up Photography by Julian Cremona

Author:Julian Cremona
Language: eng
Format: epub, pdf
ISBN: 9781785004667
Publisher: Crowood

Fig. 5.16

Diagram of the dark field set up in Fig. 5.15.

Achieving dark field on a microscope is quite straightforward and has been well documented. It is based on a ‘stop’ filter placed in the path of light before entering the condenser. Some universal condensers have these permanently fitted; they are just rotated into place instead of bright field lighting. If not, filters can be bought or simply made. As a ring of light is required, the filter has a large black spot (the stop) in the middle surrounded by a clear area that produces the light ring. There should be the totally blacked-out arrangement, so that the specimen is only lit from below. The specimen will then have a dark background and the transparent a filter or stop holder that swings in and out under the condenser. As the transmitted light passes up from the field diaphragm, the rays will be blocked in the centre and only a cylinder of light now enters the condenser to be focused on the specimen. If a blue spot is used instead of the black in the centre, a particularly super effect can be created, referred to as Rheinberg illumination.

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