In the early days of cinema, stage lighting was designed to accommodate an inherently orthochromatic filmstock sensitive mainly to blue-green energy. Thus daylight was a very efficient source, followed by such artificial lights as Mercury vapor and arc lights. Even though the image presented to the audience was monochromatic black and white (though sometimes tinted sepia or some such), the original scene was, of course, alive with color (or, at least comprised of many wavelengths!). Trying to render a natural looking world for the cinema audience was an ordeal, marked by quite strange makeup and art direction choices.  

The advent of panchromatic film with its much broader spectrum of sensitivity therefore represented a huge advance.  But it required a concomitant breakthrough in stage lighting. That breakthrough was incandescent light which provided a broad and continuous spectra` (essentially a black body)  to match the broad sensitivity of the new filmstock. 

When color film was produced, it soon became available in two basic types; Daylight balance and Tungsten balance (designed for the continuous black body illuminant at 32K). Thus for essentially the rest of the century, cinema enjoyed this sublime synergy that provided an utterly dependable basis from which to launch an infinitely variable artistic vision of our world.  A cinematographer was able to predict quite accurately what the effect of using a particular filter would be.

In recent years, that chromatic stability has been thrown into chromatic chaos by the introduction of discontinuous discharge lighting. Fluorescent and more recently SSL lights exhibiting widely differing spectral output, have been promoted for cinema resulting in inconsistent and often unpredictable color rendition. While we do have some very powerful post-production resources available to us, even these cannot overcome the consequences of many of these new lighting instruments.

The Solid State Lighting Project is a continuation of a project undertaken at the Academy Sci-Tech Council several years ago. Along with the continued study of SSL spectral power distribution, the project is now exploring the prospect of variable luminance or ‘flicker’ in LED’s, a phenomena associated previously with Fluorescents.

 

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