IMAGING SYSTEM WITH AUTOMATIC CONVERSION GAIN SELECTION

An image sensor may include an image pixel array. The image sensor may be provided with automatic conversion gain selection on a pixel-by-pixel basis to produce a high-dynamic-range image. Each image pixel may include a capacitor and a conversion gain transistor coupled in series between a power supply line and a floating diffusion node. The conversion gain transistor may be coupled to a control line through a gating transistor. The gating transistor may have a gate connected to a row select line. The image pixel may have an output line that is coupled to a column amplifier and a comparator. The column amplifier may generate a difference voltage based on reset and image signals. The comparator may compare the difference voltage with a predetermined threshold to determine whether to place the selected pixel in a high or low conversion gain mode.