Device for dividing a white light beam (14, 56) into a plurality of elementary beams of determined colour, said device being integrated into a chromatic analysis device for the colour printing of photographies, comprising an optical sensor (15-17) and a plurality of photosensitive sensors (24-26), each sensor allowing to collect the reflected light (28, 30, 31) by means of an optical system (21-23), to convert into an electric signal the light signal as received, and finally to amplify it (35-37); the device including also a unit (38, 39) for processing the amplified electric signals. The device is characterized in that the optical system is comprised of a plurality of dichroic filters (21-23), of complementary color, which are parallel and inclined on the optical axis (B) of the emergent beam (18), each filter reflecting the light quantity corresponding to the colour of said filter and allowing light in other colours to pass. Application to installations for printing photographic prints.