statues. The model average luminances are B ~0.24 cd\ m², G ~4 cd\m², W ~11.84 cd\m² and the direct wall average luminances are B ~0.13 cd\m², G ~5.29 cd\m², W ~19.12 cd\m² (Figure 5). General results: The collected data can be used to define the luminance levels of the statues and backgrounds in a dimly illuminated surrounding gallery. Generally speaking, the statue needs higher illuminance than the background. Nevertheless, the background may have more luminance than the statue, and this depends on the color values of both the statue and background. In particular, dark statues are preferred with a higher illuminance than bright statues and they reflect less luminance than bright statues. By contrast, dark backgrounds are preferred with less illuminance, while bright backgrounds are preferred with more illuminance. Additionally, the preferred luminance of the dark tone statue was less affected by the change of background color value and/or luminance than the bright statue. To summarize, the visual system cannot perceive a surface without evaluating its lightness and surface brightness. However, most perceptual models typically use five factors to govern the mapping of luminance as stimulus to brightness as response: object luminance, surrounding luminance, state of adaptation, gradient, and spectral content. Accordingly, such models also have to take into account the perceptual dimension of lightness. Since brightness, like all other perceptual features, is not something that can be measured directly, our experiments need to be repeated with a large number of observers to accurately verify the results. Also, we have to keep in mind that conducting the experiments in other conditions (e.g. where exhibits’ properties change, the surrounding configuration changes, and for different adaptation states) will alter the results, but will not change experiment’s main findings.
Figures: 1 The five grayscale statues in the experiment 2 Three different experiments 3 (Figure 1) The museum cases the research is concerned with. Left: the artefacts are highlighted in a dim gallery. Mummy Museum, Luxor, Egypt. Right: Two dark statues, the one on the left presented against a dark background (Luxor Museum, Luxor, Egypt), the other against a bright background (Egyptian Museum, Berlin, Germany).
Jahrbuch der Fakultät für Architektur, TUM mit einem Schwerpunkt auf Forschung und Entwicklung