Image sensor with a successive approximation A/D converter that automatically compensates for black level and provides a signal indicative of the difference between the reset level and the signal level. Black level for each of a plurality of color pixels may be obtained. This may be obtained from, for example, an image sensor with intentionally darkened pixels. Levels from these pixels are sampled, and an average of these pixels is used to form a black level for similarly-colored pixels. That black level is stored, and used to drive a D/A converter. Another D/A converter forms the actual conversion, and is compared to a reference. The reference is selected such that the output signal is automatically compensated for black level, and also corresponds to the difference between signal and reset.