1. An image sensor comprising: a plurality of micro-lenses arranged in rows and columns; and a light-sensitive semiconductor region disposed adjacent the micro-lenses without additional lensing therebetween and having a plurality of sub-regions arranged in rows and columns that correspond to the rows and columns of the micro-lenses, each of the sub-regions having a plurality of uniformly sized light-sensitive elements disposed to receive light collected by a respective one of the micro-lenses and that generate respective signal levels in correspondence with sensing respective numbers of photons.