A spectrometer may include: an input configured to receive optical radiation; a dispersion element configured to disperse by wavelength the optical radiation passing from the input; an output; and/or a spatial light modulator (SLM) configured to receive a wavelength region of the optical radiation dispersed by the dispersion element, and configured to selectively direct wavelength portions of the received wavelength region to the output. The input may be configured to provide a plurality of entrance field stops by which the dispersion element is, in use, illuminated. Each of the plurality of entrance field stops may cooperate with the dispersion element to generate a different dispersed wavelength region at the SLM.