Thursday, September 2, 2021

The wonders of technology - selective chromatic lighting

When it comes to lighting museums, particularly those with sensitive cultural treasures, one of the most frequent challenges can be how to balance the desire to display light sensitive objects to the public with the need to preserve those objects from the degradation caused by exposure to light. Numerous techniques and standards have been developed over the years with which we have all become familiar, but an article in the latest edition of Lighting Research & Technology offers the possibility of an interesting out-of-the-box option. 

The article, in general, poses the idea of illuminating highly sensitive objects with what it calls “selective chromatic lighting”, which amounts to lighting an object with only the wavelengths of light which would be reflected by that object.  Essentially, we are talking about lighting an object with a high resolution photographic projection of the object itself to reduce damaging light absorption. 

While, in practice, this may be prohibitive on a large scale for multiple reasons, on a small scale it does pose some interesting possibilities. Imagine, for example, that you had a highly sensitive handwritten letter, black ink on paper, which would ordinarily be limited to 30 lux or less. The concern, beyond a yellowing of the paper, would be the fading of the pigment in the handwriting which would reduce the legibility over time. The possibility posed by the article is this: What if you illuminated the letter with a high definition photograph of the letter projected from an LED light source and aligned with the original. Then, for all intents and purposes, you are only illuminating the empty white page and minimizing the light which would fall on the text itself. While certainly not an everyday solution, it is one which current technologies make much more conceivable than in days gone by. 

If you have some time we recommend the article. A link to the abstract is provided below.