LOOKING AT HOLOGRAMS
In the early days of holography, holograms had to be viewed in laser light and consequently the images were the colour of the lasers used, usually red or green. Since the development of white light viewable holograms, a considerable number of techniques have been developed giving the artists and designers who use holography a much wider range of visual styles and effects to work with.
Steve Benton, who invented the white light transmission or Rainbow hologram, was particularly influential as his invention is the basis of the Embossed Hologram which is more widely used than any other type, on security documents, packaging and for a vast range of promotional and decorative purposes.
This exhibition includes a selection of larger format rainbow holograms and if you move up and down in front of these you will observe how the colour changes through the spectrum according to your height, (hence the name 'rainbow'). Using several exposures it is possible to create multicolour images by overlaying the rainbows at different reference angles. A variation of the technique can also be used to create achromatic or colourless (black and white) images.
Rainbow holograms are designed to be illuminated by transmitted light passing through them, but by putting a mirror or layer of silver behind them they can be lit from the front like reflection holograms.
Classic reflection holograms are generally single coloured (usually green or orange), but by manipulating the holographic emulsion with chemical solutions and multiple exposures it is possible to create pseudo-colour holograms. These have more than one colour but are not true to life.
The pursuit of true colour in holograms is like the search from the Holy Grail and many routes have been taken in the quest to achieve it. The purest type of true colour holograms uses Red, Green and Blue lasers to expose the holographic recording material but convincing results can also be achieved by using the stereogram technique. This involves making a short sequence of colour film or video, recording the subject from different angles, often using a camera that travels along a rail. This film is then separated into its RGB constituents and a sequence of holograms is made for each colour with the frames arranged in stereoscopic pairs. Viewing the end result is not unlike looking at a flip-book as a sequence of still images is presented to your eyes in quick succession as you move past the hologram, creating the impression of seamless movement.
The latest development in holography is the Digital Hologram, which also employs the stereogram technique but records the information as a complex array of pixels, each one of which contains information about the whole image.
Though immensely sophisticated from a technical point of view, digital holograms cannot yet match the clarity of the best 'analogue' holograms of the past. But because the process is more accessible to a generation comfortable with working on computers, it is likely that holography will acquire more practitioners as a result. It is to be hoped that this new generation of holographers will look back at the more 'hands-on' and craft-based skills required to make analogue holograms and be tempted to give them a try.
Visitors to the previous hologram exhibition will have seen examples of most of these types of hologram before but the intention of this show is to present a wider range of holographers and more examples of rainbow and digital holography than before. This is not exactly an art exhibition, though it does contain the work of several artists, but more of a window onto the wonderful world of holography. Our intention is to inform, to entertain, and to demonstrate the versatility of holography as multi-faceted medium that is constantly developing.
Artists in the exhibition.