An A/D converter system that has a ranging detector that receives and characterizes an input signal. The characterizing sets a coarse range selection based on a level of the input signal. A higher level input signal has a higher level ranging. An A/D converter includes a compression system that compresses based on the ranging output signal by converting different numbers of bits for different level ranging output signal. A higher level input signal is more higher compressed and produces a digital output indicative of the input signal, which is compressed by different amounts based on the ranging output signal. By scaling in this way, the resolution of the A/D converter is scaled on the basis of shot noise level of the image sensor.