In order to quantify the effect of oversampling in a pixel array, a new transfer function is defined. This transfer function is shown to provide a direct comparison between the practical performance of a pixel array with and without oversampling. It is also found to be useful for measuring the influence of different lattice structures on the array. Explicit formulas for the transfer function have also been derived for a few common types of pixel arrays. The same concepts and formulas also turned out to be useful in evaluating the performance of ordinary pixel arrays when the image is not bandlimited.