One or more techniques and/or systems are described for addressing (e.g., during calibration) pixel-by-pixel variations in an image modality that utilizes photon counting techniques, such as by adjusting a number of photons detected by certain pixels (e.g., redistributing or reallocating detected photons among pixels). Such variations may cause an effective area of one or more pixels of a detector array to be larger than the effective area of other pixels, resulting in more photons being counted by some pixels than others, which can degrade resulting images. Accordingly, photons are redistributed as provided herein so that, when exposed to substantially uniform radiation, photon counts of neighboring pixels are substantially equal, statistical noise among neighboring pixels is substantially equal, and a signal-to-noise ratio among neighboring pixels is substantially equal. By redistributing photons as described herein, a spatial uniformity and/or a modulated transfer function (MTF) associated with a detector array may be improved.