The film is organized into eight chapters:

In the following the contents of the chapters is outlined. Click on the respective icon if you have already seen the film and want to go further into the depth of the presentation and the propositions made in it.

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See for instance this supplement to the film.


Light weaves in space and shines in matter. A world of images based on contrast is created. Goethe studied simple pictures in black and white through a glass prism and found four basic kinds of spectra, complementary in pairs. To the conventional Newtonian spectrum there corresponds an inverted spectrum.


A parallel flux of light is sent through a glass prism and sweeps along a piece of white cardboard. The white band renders a flux of dispersed light visible and in this various colour spectra are produced with the help of apertures.


When the apertures are in form of plane mirrors the original light flux is divided into two complementary parts. I becomes apparent that they are aspects of one and the same phenomenon.


A short recapitulation of Newton' s demonstration from Opticks (1704), showing that a light ray, produced by letting the light from a small region of a spectrum pass through an aperture and further on through a prism, is deviated without changing its colour or spreading out into a multicoloured spectrum. Because of this it is called "monochromatic".


Now, how would the corresponding demonstration, performed on the inverted spectrum, look? Due to the principle of complementarity, any coloured ray from it, say a purple ray, should not spilt up into several colours upon passing through prism. The Norwegian physicist Torger Holtsmark clarified theoretically how an optical arrangment should be made in order to produce a "monochromatic" purple ray. The key concept is that the ray should be produed within a bright environment (whereas the newtonian monchromatic light rays are produced in a dark environment!)


To accomplish this an arrangement with two mirrors with narrow slits is used (see photo). They should be mounted strictly parallel to each other. In the film we see how they are placed into the flux of dispersed light from the main prism.


To each monochromatic light ray there corresponds a monochromatic shadow ray, having the complementary colour. The monochromatic shadow rays are a kind of coloured shadows. Evidently, in connection with images -- thus with the visual world in general -- darkness plays a role as important as light. The demonstration means a rehabilitation of darkness.


Rays of light are just images, as are the rays of shadow. The images and their colours are in light, are produced by light, but they are not light itself. Goethe says: "First and foremost, let us remind ourselves that we wander in the realm of images"



Speaker text in three languages: English, German and Swedish

Length: 17 min, Aspect ratio 4:3, DVD Video PAL

Including a booklet with foreword by Prof. Johannes Grebe-Ellis and an explanatory text by Pehr Sällström: "The Enigma of the Purple-Ray". Given in English as well as German. For the corresponding Swedish text, see here -->

Published by DRUCKtuell, Druck- und Medienzentrum Gerlingen GmbH


Price: 21.00€

ISBN 978-3-940606-60-0

PSColour\contents-uk.htm per 2010-02-14 updated 2014-11-03