An ultraviolet-visible spectrophotometry (UV/Vis) high-performance liquid chromatography (HPLC) photometer includes a nano flow cell in which a light source feeds a reference light channel and a sample light channel, a reference photodiode for evaluating the reference light channel, and a sample photodiode for evaluating the sample light channel, which extends through the nano flow cell. To create a photometer whose signal evaluation is improved, respective effective exposure times of the sample photodiode and the reference photodiode are settable separately from one another.