Abstract: An attenuating optical shutter for high speed spectral analysis of an optical radiation band so as to derive N wavelength-dependent portions thereof. The attenuating optical shutter incorporates an optical shutter body including N shutter segments, each selectably switchable between a first substantially transparent and a second substantially opaque optical state, and a multi-zone attenuator comprising N optical attenuating zones each having a different predetermined wavelength-dependent attenuation characteristic. Each of the shutter segments is optically interconnected with a respective one of the N optical attenuating zones of the multi-zone attenuator thus forming N respective cells of the attenuating optical shutter. Such an attenuating optical shutter finds particular application in a spectrometer. A method for determining the spectral function of a sample using the attenuating optical shutter is also described.