A spectrophotometer has a first photodetector (24) and a second photodetector (25) which is displaced spatially from the first photodetector in the direction of increasing wavelength in the spectrum. At any given time the second photodetector receives light at a wavelength which is substantially greater than that being received simultaneously by the first photodetector at that time. The first photodetector has first range of wavelengths over which it is operable and a first upper operating limit, and the second photodetector has a second range of wavelengths over which it is operable and a second upper operating limit, the second range overlapping the first range and the second upper operating limit being greater than the first upper operating limit. Thus the range of operation is extended, and data in two different ranges is processed simultaneously. The spectrophotometer comprises a housing (1) containing a light source (11), a monochromator (15, 16, 18) and the photodetectors, there being a fibre optic connected to a probe (2) for transmitting light from the light source to a sample to be analysed and receiving light from the sample. Optical components are mounted to a chassis (26) of the housing rigidly, the chassis being connected to the housing by shock absorbing mounts (28, 29). The light source is mounted to the housing by means of an adjuster (24) providing for adjustment laterally with respect to the optical axis of the light source.