Illumination plays an important role in the image capture process. Too little or too much energy in particular wavelengths can impact the scene appearance in a way that is difficult to manage by color constancy post processing methods. We use an adjustable multispectral flash to modify the spectral illumination of a scene. The flash is composed of a small number of narrowband lights, and the imaging system takes a sequence of images of the scene under each of those lights. Pixel data is used to estimate the spectral power distribution of the ambient light, and to adjust the flash spectrum either to match or to complement the ambient illuminant. The optimized flash spectrum can be used in subsequent captures, or a synthetic image can be computationally rendered from the available data. Under extreme illumination conditions images captured with the matching flash have no color cast, and the complementary flash produces more balanced colors. The proposed system also improves the quality of images captured in underwater environments.
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