An apparatus includes a source of spectral light indicative of a sample to be measured, a camera to sense a spectrum, and a chromatic dispersion device to spatially separate light from the sample to be measured into the spectrum. The camera includes a sensor and control circuitry. The sensor is one of a CCD line sensor and a CCD TDI sensor. The sensor includes a plurality of pixels, a conversion node, a readout register coupled to the conversion node and a reset gate coupled to the conversion node. The control circuitry is capable of shifting the readout register to transfer charges onto the conversion node and capable of controlling the reset gate to reset the conversion node at varying intervals enabling the conversion node to integrate charges from a varying number of elements of the readout register.