This article and the following one will discuss the effect on resolution of digitizing a continuous optical image.

The sampling process carried out by the sensor results in digital values corresponding to an intensity at each pixel’s location.  These so-called Data Numbers are stored ideally as-is in the raw file and are proportional to infinitesimal point samples of a new continuous image: the optical image smoothed by the characteristics of the pixels’ effective active area, known as the pixel aperture function.

Smoothing by a finite pixel area reduces resolution. (read more…)