An apparatus includes analog-to-digital (A/D) conversion circuitry coupled to a pixel array. The A/D conversion circuitry includes a voltage ramp generator and a set of column A/D conversion circuits. The voltage ramp generator generates a single slope voltage ramp in a first state and a multiple slope voltage ramp in a second state. The set of column A/D conversion circuits is coupled with the voltage ramp generator. The apparatus further includes calibration circuitry coupled with the set of column A/D conversion circuits and operable to determine digital calibration data to adjust digital image data. The calibration circuitry provides analog calibration data that spans a calibration range to the set of column A/D conversion circuits instead of the analog image data from the pixel array being provided to the set of column A/D conversion circuits.