in the photostimulable phosphor screen is read out the most important components of the read out apparatus are schematically shown in fig2 the readout apparatus comprises an electronic signal processing unit 21 a scanning unit 22 and an electronic memory device 23 the components of scanning unit 22 are shown in fig3 scanning unit 22 comprises a linear light source 8 comprising an array of laser sources a linear array of sensor elements 9 means not shown for transporting photostimulable phosphor screen 1 and the array of solid state sensor elements 9 relative to each other and light guiding means 10 for guiding light emitted by the photostimulable phosphor screen upon stimulation towards sensor array 9 signal processing unit 21 is programmed for reading data among which the exposure class which are stored in rf tag 5 which is provided on the cassette conveying the stimulable phosphor screen in another embodiment the rf tag is replaced by an eeprom that can be read out via galvanic contact the read out apparatus further comprises a memory device 23 memory device 23 stores for each specific exposure class a corresponding capacitance value which is to be switched into the solid state sensor circuit 8 of the scanning unit 22 the electronic circuitry 21 is programmed to read from memory device 23 the capacitance value that corresponds with an exposure class that has been read out of the rf tag 5 the electronic circuit is further programmed for controlling that the correct capacity amount is switched into the solid state sensor circuit the solid state sensor.