In one aspect, the present invention provides an active pixel sensor array with optimized matching between pixels and strength and frequency of incoming signals such as photons absorbed. The array comprises multiple pixels of individual geometry corresponds to spatial location. Each pixel full-well is adjustable via modifiable pixel conversion gain while maintaining pixel linearity. Furthermore each pixel internally stores multiple of extremely high frequency samples. Variable pixel geometry per row is very advantageous for Echelle spectrograph, where pixel heights are aligned with the spectrograph “order separator” where the resolution changes. In combination with variable geometry, externally adjustable full-well provides for superior spectral line separation in spectroscopy applications. In one embodiment multiple time windows with intermittent resets are stored within each pixel. This feature allows for the detection of extreme high frequency consecutive events without saturation such as may be the case with LIBS (Laser Induced Breakdown Spectroscopy).