1. Size determining means to determine a number of pixels in at least one dimension of a sensor array of photoelectric devices, comprising: a. readout register means for receiving charge accumulated in the sensor array; b. clock means to apply clock cycle pulses to the readout register means to read out charge from the readout register means for a predetermined number of clock cycles known to exceed a number of pixels in the at least one dimension of the sensor array; c. discontinuity detection means to determine a first discontinuity in the readout charge, representing a last active pixel in the at least one dimension of the sensor array; and d. counter means to count clock cycles between a first active pixel and the first discontinuity to determine a number of active pixels in the at least one dimension of the sensor array.