  Image sensors with nondestructive charge readout provide single-photon or
single-electron sensitivity, but at the cost of long readout times. We present
a smart readout technique to allow the use of these sensors in visible-light
and other applications that require faster readout times. The method optimizes
the readout noise and time by changing the number of times pixels are read out
either statically, by defining an arbitrary number of regions of interest (ROI)
in the array, or dynamically, depending on the charge or energy of interest
(EOI) in the pixel. This technique is tested in a Skipper CCD showing that it
is possible to obtain deep sub-electron noise, and therefore, high resolution
of quantized charge, while dynamically changing the readout noise of the
sensor. These faster, low noise readout techniques show that the skipper CCD is
a competitive technology even where other technologies such as Electron
Multiplier Charge Coupled Devices (EMCCD), silicon photo multipliers, etc. are
currently used. This technique could allow skipper CCDs to benefit new
astronomical instruments, quantum imaging, exoplanet search and study, and
quantum metrology.
