Imaging system includes pixel groups and a trigger generator to generate reset signals and a transfer signal. Each pixel group includes pixels and a programmable memory element to store a first or a second value. Each pixel includes a pixel circuit with a photodiode and a storage capacitance. The pixel circuit, the trigger generator, and the memory element are interconnected to permit the photodiode to be held at a constant voltage when the trigger generator sends the reset signal to the pixel circuit. When the reset signal is switched off, the photodiode accumulates a charge while being irradiated. When the transfer signal is received, the charge is transferred to the storage capacitance. The memory element blocks the transfer signal from arriving on all the pixel circuits when it has stored the first value and passes the transfer signal to all the pixel circuits when it has stored the second value.