Stacked chip imaging system comprising pixel array partitioned into pixel sub-arrays (PSAs) disposed in first semiconductor die and ADC circuitry including ADC circuits disposed in second semiconductor die. Each PSA is arranged into pixel groups. Each pixel group generates pixel data signals. Pixel array captures image data of first frame with first exposure time, second frame with second exposure time, third frame with third exposure time, and fourth frame with fourth exposure time. First, second, third and fourth exposure times are different. At least one of the pixel groups in each of the pixel sub-arrays is coupled to a different ADC circuit from pixels groups remaining in each of the pixel sub-arrays. ADC circuitry acquires the pixel data signals. For each frame, ADC circuits converts pixel data signal received from pixel groups respectively coupled thereto from analog to digital to generate ADC outputs. Other embodiments are also described.