AIC's 52nd Annual Meeting

Relevance and background

Preserving the integrity of historical artifacts remains a paramount concern for cultural heritage. However, stewards of heritage grapple with the material degradation over time catalyzed by environmental conditions, such as air quality, humidity, and light. Light can cause photochemical damage when directed onto light-sensitive artwork like textiles, paper-based works, or oil paintings, resulting in color fading, varnish yellowing, or undesirable color shifts.

While light is an imperative medium for human visual perception, the dichotomy it presents—between enhancing visibility and inducing damage—is at the crux of conservation endeavors, exerting a critical influence on art display within museums. The "visibility-damage dilemma" shapes the lifetime of artworks, governed by the antagonistic relationship between prolonged exposure and longevity. While prevailing museum lighting guidelines underscore the importance of curbing light exposure, it is important to acknowledge that stringent light reduction measures, while mitigating damage, may not uniformly cater to human visual perception. Under dim lighting (often 50 lux or lower), paintings may lose their inherent vibrancy, owing to the decreased sensitivity of the human visual system. Such conditions can render objects visually muted, prompting the re-evaluation of universally adopting reduced light levels as a catch-all solution for both conservation and visual appeal.

Purpose and hypothesis

A promising novel application is the optimization of light using projection mapping techniques, which can improve the viewing experience while simultaneously reducing degradation caused by light. Previous studies show that light source spectra can be spectrally optimized to reduce light absorbed by materials, only emitting light that is reflected off of surfaces. We hypothesize that light projection systems can be used to go beyond visual enhancement, embracing the mitigation of photodegradation-induced color desaturation or compensating for low light levels.

Methods and outcomes

Our research started with computational simulations aimed at quantifying reduced damages. Linear optimization methods gauged the appearance of 15 color samples under different illuminants, yielding energy savings up to 71% without perceptible color shifts. Extending this exploration into heritage conservation, we used a seven-channel LED system targeting the preservation of monochromatic oil paintings, demonstrating the feasibility of halving damage and energy consumption without inducing discernible color shifts. In a follow up study, an absorption-reducing light projection prototype was tailored for Joaquín Sorolla's painting "Walk on the beach". This RGB projector-based system utilized point-by-point light projection to curtail damage by up to 49% compared to daylight, and up to 67% compared to incandescent illumination, all the while preserving color fidelity. Finally, we conducted a vision experiment to test the appearance of artwork under light projection to test user acceptance.

These advancements herald the path toward spatially and spectrally precise light optimization, culminating in prototypes attuned to the spatial complexities of multi-colored artworks. This comprehensive exploration not only underscores the intricate interplay between light, preservation, and visual aesthetics but also supports evidence for the potential of light projection systems as transformative tools within the realms of conservation.