An image sensor may be implemented using a stitched image sensor die. The stitched image sensor die may be formed from a step and repeat exposure process using a set of physical tiles in a reticle set. The physical tiles may include a center tile forming pixel circuitry on the image sensor die and peripheral tiles forming non-pixel circuitry on the image sensor die. Each of the physical tiles may be sized based on an integer multiple of a virtual unit tile. As such, the physical tiles may have dimensions that are not required to be an integer multiple of the smallest physical tile. The step and repeat exposure process may use the unit lengths of the virtual unit tile to properly position the die relative to the processing tools.