Dark current reduction for image sensor having electronic global shutter and image storage capacitors

An image sensor has an array of pixels, each pixel having an associated shutter transistor coupled to transfer a charge dependent on light exposure of the pixel onto an image storage capacitor, the image-storage capacitors being configured to be read into an analog to digital converter. The shutter transistors are P-type transistors in N-wells, the wells held at an analog power voltage to reduce sensitivity of pixels to dark current; in an alternative embodiment the shutter transistors are N-type transistors in P-wells, the wells held at an analog ground voltage.