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Fading behavior of undyed feathers has not received much attention in conservation literature and as a result feathers are categorized with other natural materials as being fugitive to display lighting, based on anecdotal evidence. The authors investigated Red-shafted Flicker feathers, which have carotenoid-based colorant systems and significance in North American native regalia, to demonstrate how lighting guidelines could be informed by a multivariate approach that considers material sensitivity, properties of value, and use before entering a museum collection. Ornithological literature reviewed demonstrates that feathers are highly differentiated in their sources of coloration, which include chemistry, structure, diet, age and,gender, all resulting in varying responses to illumination. The authors explore the value placed on color by original fabricators, and how use and attitudes toward color contribute to the collections for which we assume stewardship. Red-shafted Flicker feathers were exposed to equivalent photometric doses in order to compare results from window-fading and microfading to Blue Wool Standards. Results indicate color changes more stable than Blue Wool 1 and 2, with ultraviolet radiation playing a significant role in fading. Microfading is beneficial for measuring color change because the variability within and between feathers is eliminated as the sample site remains unvaried.

A simple optical technique is described that allows for the direct whole-field visualization of anti-nodal patterns in noisy environments. The technique involves the combination of defocused laser speckle imaging with the laser speckle contrast analysis (LASCA) algorithm to relate local contrast reduction of a laser speckle pattern to the magnitude of the gradient vectors that arise due to the tilt deflection of a vibrating surface. The method requires no reference beam and is tolerant of environmental noise. The sensitivity of the technique is a direct function of the degree of defocus of the speckle pattern and thus can be readily adjusted. By ratioing the instantaneous contrast to the reference image contrast, a simple method for thresholding the noise floor (noise at reference state) is attained, thus increasing the method's tolerance to ambient disturbances. Results from forced vibration via acoustic excitation of a square and rectangular membrane—with and without simultaneous white noise excitation—are shown. Results are compared to theoretical predictions for an ideal membrane, with good agreement.