Electronically controlled graduated density filters in stacked image sensors

In a digital camera having an imaging array including a plurality of pixels arranged in rows and columns, the digital camera further having a mechanical shutter having an open position allowing light to illuminate the imaging array and a closed position blocking light from illuminating the imaging array, a method for performing neutral density filtering of images captured by the imaging array, the method comprising:

• opening the mechanical shutter;
• operating each row in the array by:
• resetting all of the pixel sensors in the row;
• starting exposure for all of the pixel sensors in the row;
• closing the mechanical shutter;
• reading pixel values from the plurality of pixels in the pixel array at a time after the mechanical shutter has closed, the time being unrelated to a time at which any pixel-select signal was de-asserted;
• and
• wherein the interval of time between starting exposure for all of the pixel sensors in the row and closing the mechanical shutter for each individual row is a function of a neutral-density-filter function applied to an image to be captured.