The invention relates to a radiation detector (100) comprising a converter element (113) with an array (120) of first electrodes (121) for sampling electrical signals generated by incident radiation (X). With a connection circuit (130), at least two first electrodes (121) can selectively be coupled to a common readout unit (141) according to a given connection pattern (CP1). The effective pixel size along the path of incident radiation (X) can thus be adapted to the distribution of electrical signals, which is usually determined by the spectral composition of the incident radiation.